From 2c694e4c081fa4d66e539c6700f179d98bb5d30f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Arma=C3=ABl=20Gu=C3=A9neau?= <armael.gueneau@ens-lyon.org>
Date: Mon, 15 Apr 2024 17:58:04 +0200
Subject: [PATCH] use a builtin SMTP client instead of sendmail to send alerts

---
 Cargo.lock  | 688 +++++++---------------------------------------------
 Cargo.toml  |   2 +-
 src/main.rs |  47 +++-
 3 files changed, 123 insertions(+), 614 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index b7ad1ab..52bc069 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -36,203 +36,6 @@ version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0942ffc6dcaadf03badf6e6a2d0228460359d5e34b57ccdc720b7382dfbd5ec5"
 
-[[package]]
-name = "async-channel"
-version = "1.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "81953c529336010edd6d8e358f886d9581267795c61b19475b71314bffa46d35"
-dependencies = [
- "concurrent-queue",
- "event-listener 2.5.3",
- "futures-core",
-]
-
-[[package]]
-name = "async-channel"
-version = "2.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f28243a43d821d11341ab73c80bed182dc015c514b951616cf79bd4af39af0c3"
-dependencies = [
- "concurrent-queue",
- "event-listener 5.3.0",
- "event-listener-strategy 0.5.1",
- "futures-core",
- "pin-project-lite",
-]
-
-[[package]]
-name = "async-executor"
-version = "1.10.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5f98c37cf288e302c16ef6c8472aad1e034c6c84ce5ea7b8101c98eb4a802fee"
-dependencies = [
- "async-lock 3.3.0",
- "async-task",
- "concurrent-queue",
- "fastrand 2.0.2",
- "futures-lite 2.3.0",
- "slab",
-]
-
-[[package]]
-name = "async-global-executor"
-version = "2.4.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "05b1b633a2115cd122d73b955eadd9916c18c8f510ec9cd1686404c60ad1c29c"
-dependencies = [
- "async-channel 2.2.0",
- "async-executor",
- "async-io 2.3.2",
- "async-lock 3.3.0",
- "blocking",
- "futures-lite 2.3.0",
- "once_cell",
-]
-
-[[package]]
-name = "async-io"
-version = "1.13.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0fc5b45d93ef0529756f812ca52e44c221b35341892d3dcc34132ac02f3dd2af"
-dependencies = [
- "async-lock 2.8.0",
- "autocfg",
- "cfg-if",
- "concurrent-queue",
- "futures-lite 1.13.0",
- "log",
- "parking",
- "polling 2.8.0",
- "rustix 0.37.27",
- "slab",
- "socket2 0.4.10",
- "waker-fn",
-]
-
-[[package]]
-name = "async-io"
-version = "2.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcccb0f599cfa2f8ace422d3555572f47424da5648a4382a9dd0310ff8210884"
-dependencies = [
- "async-lock 3.3.0",
- "cfg-if",
- "concurrent-queue",
- "futures-io",
- "futures-lite 2.3.0",
- "parking",
- "polling 3.6.0",
- "rustix 0.38.32",
- "slab",
- "tracing",
- "windows-sys 0.52.0",
-]
-
-[[package]]
-name = "async-lock"
-version = "2.8.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "287272293e9d8c41773cec55e365490fe034813a2f172f502d6ddcf75b2f582b"
-dependencies = [
- "event-listener 2.5.3",
-]
-
-[[package]]
-name = "async-lock"
-version = "3.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d034b430882f8381900d3fe6f0aaa3ad94f2cb4ac519b429692a1bc2dda4ae7b"
-dependencies = [
- "event-listener 4.0.3",
- "event-listener-strategy 0.4.0",
- "pin-project-lite",
-]
-
-[[package]]
-name = "async-process"
-version = "1.8.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ea6438ba0a08d81529c69b36700fa2f95837bfe3e776ab39cde9c14d9149da88"
-dependencies = [
- "async-io 1.13.0",
- "async-lock 2.8.0",
- "async-signal",
- "blocking",
- "cfg-if",
- "event-listener 3.1.0",
- "futures-lite 1.13.0",
- "rustix 0.38.32",
- "windows-sys 0.48.0",
-]
-
-[[package]]
-name = "async-signal"
-version = "0.2.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9e47d90f65a225c4527103a8d747001fc56e375203592b25ad103e1ca13124c5"
-dependencies = [
- "async-io 2.3.2",
- "async-lock 2.8.0",
- "atomic-waker",
- "cfg-if",
- "futures-core",
- "futures-io",
- "rustix 0.38.32",
- "signal-hook-registry",
- "slab",
- "windows-sys 0.48.0",
-]
-
-[[package]]
-name = "async-std"
-version = "1.12.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62565bb4402e926b29953c785397c6dc0391b7b446e45008b0049eb43cec6f5d"
-dependencies = [
- "async-channel 1.9.0",
- "async-global-executor",
- "async-io 1.13.0",
- "async-lock 2.8.0",
- "async-process",
- "crossbeam-utils",
- "futures-channel",
- "futures-core",
- "futures-io",
- "futures-lite 1.13.0",
- "gloo-timers",
- "kv-log-macro",
- "log",
- "memchr",
- "once_cell",
- "pin-project-lite",
- "pin-utils",
- "slab",
- "wasm-bindgen-futures",
-]
-
-[[package]]
-name = "async-task"
-version = "4.7.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fbb36e985947064623dbd357f727af08ffd077f93d696782f3c56365fa2e2799"
-
-[[package]]
-name = "async-trait"
-version = "0.1.79"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a507401cad91ec6a857ed5513a2073c82a9b9048762b885bb98655b306964681"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "atomic-waker"
-version = "1.1.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1505bd5d3d116872e7271a6d4e16d81d0c8570876c8de68093a09ac269d8aac0"
-
 [[package]]
 name = "autocfg"
 version = "1.2.0"
@@ -258,7 +61,7 @@ dependencies = [
  "aws-smithy-types",
  "aws-types",
  "bytes",
- "fastrand 2.0.2",
+ "fastrand",
  "hex",
  "http 0.2.12",
  "hyper",
@@ -297,7 +100,7 @@ dependencies = [
  "aws-smithy-types",
  "aws-types",
  "bytes",
- "fastrand 2.0.2",
+ "fastrand",
  "http 0.2.12",
  "http-body 0.4.6",
  "percent-encoding",
@@ -327,7 +130,7 @@ dependencies = [
  "aws-smithy-xml",
  "aws-types",
  "bytes",
- "fastrand 2.0.2",
+ "fastrand",
  "hex",
  "hmac",
  "http 0.2.12",
@@ -531,7 +334,7 @@ dependencies = [
  "aws-smithy-runtime-api",
  "aws-smithy-types",
  "bytes",
- "fastrand 2.0.2",
+ "fastrand",
  "h2",
  "http 0.2.12",
  "http-body 0.4.6",
@@ -541,7 +344,7 @@ dependencies = [
  "once_cell",
  "pin-project-lite",
  "pin-utils",
- "rustls",
+ "rustls 0.21.10",
  "tokio",
  "tracing",
 ]
@@ -668,12 +471,6 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
-[[package]]
-name = "bitflags"
-version = "2.5.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf4b9d6a944f767f8e5e0db018570623c85f3d925ac718db4e06d0187adb21c1"
-
 [[package]]
 name = "block-buffer"
 version = "0.10.4"
@@ -683,28 +480,6 @@ dependencies = [
  "generic-array",
 ]
 
-[[package]]
-name = "blocking"
-version = "1.5.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a37913e8dc4ddcc604f0c6d3bf2887c995153af3611de9e23c352b44c1b9118"
-dependencies = [
- "async-channel 2.2.0",
- "async-lock 3.3.0",
- "async-task",
- "fastrand 2.0.2",
- "futures-io",
- "futures-lite 2.3.0",
- "piper",
- "tracing",
-]
-
-[[package]]
-name = "bumpalo"
-version = "3.16.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "79296716171880943b8470b5f8d03aa55eb2e645a4874bdbb28adb49162e012c"
-
 [[package]]
 name = "bytes"
 version = "1.6.0"
@@ -743,15 +518,6 @@ dependencies = [
  "stacker",
 ]
 
-[[package]]
-name = "concurrent-queue"
-version = "2.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d16048cd947b08fa32c24458a22f5dc5e835264f689f4f5653210c69fd107363"
-dependencies = [
- "crossbeam-utils",
-]
-
 [[package]]
 name = "const-oid"
 version = "0.9.6"
@@ -801,12 +567,6 @@ dependencies = [
  "cfg-if",
 ]
 
-[[package]]
-name = "crossbeam-utils"
-version = "0.8.19"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "248e3bacc7dc6baa3b21e405ee045c3047101a49145e7e9eca583ab4c2ca5345"
-
 [[package]]
 name = "crypto-bigint"
 version = "0.4.9"
@@ -929,75 +689,6 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
 
-[[package]]
-name = "errno"
-version = "0.3.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a258e46cdc063eb8519c00b9fc845fc47bcfca4130e2f08e88665ceda8474245"
-dependencies = [
- "libc",
- "windows-sys 0.52.0",
-]
-
-[[package]]
-name = "event-listener"
-version = "2.5.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0206175f82b8d6bf6652ff7d71a1e27fd2e4efde587fd368662814d6ec1d9ce0"
-
-[[package]]
-name = "event-listener"
-version = "3.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d93877bcde0eb80ca09131a08d23f0a5c18a620b01db137dba666d18cd9b30c2"
-dependencies = [
- "concurrent-queue",
- "parking",
- "pin-project-lite",
-]
-
-[[package]]
-name = "event-listener"
-version = "4.0.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "67b215c49b2b248c855fb73579eb1f4f26c38ffdc12973e20e07b91d78d5646e"
-dependencies = [
- "concurrent-queue",
- "parking",
- "pin-project-lite",
-]
-
-[[package]]
-name = "event-listener"
-version = "5.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d9944b8ca13534cdfb2800775f8dd4902ff3fc75a50101466decadfdf322a24"
-dependencies = [
- "concurrent-queue",
- "parking",
- "pin-project-lite",
-]
-
-[[package]]
-name = "event-listener-strategy"
-version = "0.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "958e4d70b6d5e81971bebec42271ec641e7ff4e170a6fa605f2b8a8b65cb97d3"
-dependencies = [
- "event-listener 4.0.3",
- "pin-project-lite",
-]
-
-[[package]]
-name = "event-listener-strategy"
-version = "0.5.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "332f51cb23d20b0de8458b86580878211da09bcd4503cb579c225b3d124cabb3"
-dependencies = [
- "event-listener 5.3.0",
- "pin-project-lite",
-]
-
 [[package]]
 name = "eyre"
 version = "0.6.12"
@@ -1008,15 +699,6 @@ dependencies = [
  "once_cell",
 ]
 
-[[package]]
-name = "fastrand"
-version = "1.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e51093e27b0797c359783294ca4f0a911c270184cb10f85783b118614a1501be"
-dependencies = [
- "instant",
-]
-
 [[package]]
 name = "fastrand"
 version = "2.0.2"
@@ -1063,40 +745,6 @@ version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dfc6580bb841c5a68e9ef15c77ccc837b40a7504914d52e47b8b0e9bbda25a1d"
 
-[[package]]
-name = "futures-io"
-version = "0.3.30"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a44623e20b9681a318efdd71c299b6b222ed6f231972bfe2f224ebad6311f0c1"
-
-[[package]]
-name = "futures-lite"
-version = "1.13.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "49a9d51ce47660b1e808d3c990b4709f2f415d928835a17dfd16991515c46bce"
-dependencies = [
- "fastrand 1.9.0",
- "futures-core",
- "futures-io",
- "memchr",
- "parking",
- "pin-project-lite",
- "waker-fn",
-]
-
-[[package]]
-name = "futures-lite"
-version = "2.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "52527eb5074e35e9339c6b4e8d12600c7128b68fb25dcb9fa9dec18f7c25f3a5"
-dependencies = [
- "fastrand 2.0.2",
- "futures-core",
- "futures-io",
- "parking",
- "pin-project-lite",
-]
-
 [[package]]
 name = "futures-sink"
 version = "0.3.30"
@@ -1116,12 +764,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d6401deb83407ab3da39eba7e33987a73c3df0c82b4bb5813ee871c19c41d48"
 dependencies = [
  "futures-core",
- "futures-io",
  "futures-task",
- "memchr",
  "pin-project-lite",
  "pin-utils",
- "slab",
 ]
 
 [[package]]
@@ -1151,18 +796,6 @@ version = "0.28.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4271d37baee1b8c7e4b708028c57d816cf9d2434acb33a549475f78c181f6253"
 
-[[package]]
-name = "gloo-timers"
-version = "0.2.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9b995a66bb87bebce9a0f4a95aed01daca4872c050bfcb21653361c03bc35e5c"
-dependencies = [
- "futures-channel",
- "futures-core",
- "js-sys",
- "wasm-bindgen",
-]
-
 [[package]]
 name = "group"
 version = "0.12.1"
@@ -1309,7 +942,7 @@ dependencies = [
  "httpdate",
  "itoa",
  "pin-project-lite",
- "socket2 0.5.6",
+ "socket2",
  "tokio",
  "tower-service",
  "tracing",
@@ -1326,7 +959,7 @@ dependencies = [
  "http 0.2.12",
  "hyper",
  "log",
- "rustls",
+ "rustls 0.21.10",
  "rustls-native-certs",
  "tokio",
  "tokio-rustls",
@@ -1358,69 +991,35 @@ dependencies = [
  "hashbrown",
 ]
 
-[[package]]
-name = "instant"
-version = "0.1.12"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7a5bbe824c507c5da5956355e86a746d82e0e1464f65d862cc5e71da70e94b2c"
-dependencies = [
- "cfg-if",
-]
-
-[[package]]
-name = "io-lifetimes"
-version = "1.0.11"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eae7b9aee968036d54dce06cebaefd919e4472e753296daccd6d344e3e2df0c2"
-dependencies = [
- "hermit-abi",
- "libc",
- "windows-sys 0.48.0",
-]
-
 [[package]]
 name = "itoa"
 version = "1.0.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49f1f14873335454500d59611f1cf4a4b0f786f9ac11f4312a78e4cf2566695b"
 
-[[package]]
-name = "js-sys"
-version = "0.3.69"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "29c15563dc2726973df627357ce0c9ddddbea194836909d655df6a75d2cf296d"
-dependencies = [
- "wasm-bindgen",
-]
-
-[[package]]
-name = "kv-log-macro"
-version = "1.0.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0de8b303297635ad57c9f5059fd9cee7a47f8e8daa09df0fcd07dd39fb22977f"
-dependencies = [
- "log",
-]
-
 [[package]]
 name = "lettre"
 version = "0.11.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "47460276655930189e0919e4fbf46e46476b14f934f18a63dd726a5fb7b60e2e"
 dependencies = [
- "async-std",
- "async-trait",
+ "base64 0.22.0",
  "chumsky",
  "email-encoding",
  "email_address",
- "fastrand 2.0.2",
- "futures-io",
- "futures-util",
+ "fastrand",
  "httpdate",
  "idna",
  "mime",
+ "nom",
+ "percent-encoding",
  "quoted_printable",
+ "rustls 0.23.4",
+ "rustls-pemfile 2.1.2",
+ "socket2",
  "tokio",
+ "url",
+ "webpki-roots",
 ]
 
 [[package]]
@@ -1429,26 +1028,11 @@ version = "0.2.153"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c198f91728a82281a64e1f4f9eeb25d82cb32a5de251c6bd1b5154d63a8e7bd"
 
-[[package]]
-name = "linux-raw-sys"
-version = "0.3.8"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef53942eb7bf7ff43a617b3e2c1c4a5ecf5944a7c1bc12d7ee39bbb15e5c1519"
-
-[[package]]
-name = "linux-raw-sys"
-version = "0.4.13"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "01cda141df6706de531b6c46c3a33ecca755538219bd484262fa09410c13539c"
-
 [[package]]
 name = "log"
 version = "0.4.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "90ed8c1e510134f979dbc4f070f87d4313098b704861a105fe34231c70a3901c"
-dependencies = [
- "value-bag",
-]
 
 [[package]]
 name = "lru"
@@ -1481,6 +1065,12 @@ version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
 
+[[package]]
+name = "minimal-lexical"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
+
 [[package]]
 name = "miniz_oxide"
 version = "0.7.2"
@@ -1501,6 +1091,16 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "nom"
+version = "7.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d273983c5a657a70a3e8f2a01329822f3b8c8172b73826411a55751e404a0a4a"
+dependencies = [
+ "memchr",
+ "minimal-lexical",
+]
+
 [[package]]
 name = "num-conv"
 version = "0.1.0"
@@ -1573,12 +1173,6 @@ dependencies = [
  "sha2",
 ]
 
-[[package]]
-name = "parking"
-version = "2.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bb813b8af86854136c6922af0598d719255ecb2179515e6e7730d468f05c9cae"
-
 [[package]]
 name = "percent-encoding"
 version = "2.3.1"
@@ -1597,17 +1191,6 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
-[[package]]
-name = "piper"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "668d31b1c4eba19242f2088b2bf3316b82ca31082a8335764db4e083db7485d4"
-dependencies = [
- "atomic-waker",
- "fastrand 2.0.2",
- "futures-io",
-]
-
 [[package]]
 name = "pkcs8"
 version = "0.9.0"
@@ -1618,37 +1201,6 @@ dependencies = [
  "spki",
 ]
 
-[[package]]
-name = "polling"
-version = "2.8.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4b2d323e8ca7996b3e23126511a523f7e62924d93ecd5ae73b333815b0eb3dce"
-dependencies = [
- "autocfg",
- "bitflags 1.3.2",
- "cfg-if",
- "concurrent-queue",
- "libc",
- "log",
- "pin-project-lite",
- "windows-sys 0.48.0",
-]
-
-[[package]]
-name = "polling"
-version = "3.6.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e0c976a60b2d7e99d6f229e414670a9b85d13ac305cc6d1e9c134de58c5aaaf6"
-dependencies = [
- "cfg-if",
- "concurrent-queue",
- "hermit-abi",
- "pin-project-lite",
- "rustix 0.38.32",
- "tracing",
- "windows-sys 0.52.0",
-]
-
 [[package]]
 name = "powerfmt"
 version = "0.2.0"
@@ -1757,33 +1309,6 @@ dependencies = [
  "semver",
 ]
 
-[[package]]
-name = "rustix"
-version = "0.37.27"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fea8ca367a3a01fe35e6943c400addf443c0f57670e6ec51196f71a4b8762dd2"
-dependencies = [
- "bitflags 1.3.2",
- "errno",
- "io-lifetimes",
- "libc",
- "linux-raw-sys 0.3.8",
- "windows-sys 0.48.0",
-]
-
-[[package]]
-name = "rustix"
-version = "0.38.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "65e04861e65f21776e67888bfbea442b3642beaa0138fdb1dd7a84a52dffdb89"
-dependencies = [
- "bitflags 2.5.0",
- "errno",
- "libc",
- "linux-raw-sys 0.4.13",
- "windows-sys 0.52.0",
-]
-
 [[package]]
 name = "rustls"
 version = "0.21.10"
@@ -1792,10 +1317,25 @@ checksum = "f9d5a6813c0759e4609cd494e8e725babae6a2ca7b62a5536a13daaec6fcb7ba"
 dependencies = [
  "log",
  "ring",
- "rustls-webpki",
+ "rustls-webpki 0.101.7",
  "sct",
 ]
 
+[[package]]
+name = "rustls"
+version = "0.23.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c4d6d8ad9f2492485e13453acbb291dd08f64441b6609c491f1c2cd2c6b4fe1"
+dependencies = [
+ "log",
+ "once_cell",
+ "ring",
+ "rustls-pki-types",
+ "rustls-webpki 0.102.2",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "rustls-native-certs"
 version = "0.6.3"
@@ -1803,7 +1343,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a9aace74cb666635c918e9c12bc0d348266037aa8eb599b5cba565709a8dff00"
 dependencies = [
  "openssl-probe",
- "rustls-pemfile",
+ "rustls-pemfile 1.0.4",
  "schannel",
  "security-framework",
 ]
@@ -1817,6 +1357,22 @@ dependencies = [
  "base64 0.21.7",
 ]
 
+[[package]]
+name = "rustls-pemfile"
+version = "2.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29993a25686778eb88d4189742cd713c9bce943bc54251a33509dc63cbacf73d"
+dependencies = [
+ "base64 0.22.0",
+ "rustls-pki-types",
+]
+
+[[package]]
+name = "rustls-pki-types"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ecd36cc4259e3e4514335c4a138c6b43171a8d61d8f5c9348f9fc7529416f247"
+
 [[package]]
 name = "rustls-webpki"
 version = "0.101.7"
@@ -1827,6 +1383,17 @@ dependencies = [
  "untrusted",
 ]
 
+[[package]]
+name = "rustls-webpki"
+version = "0.102.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "faaa0a62740bedb9b2ef5afa303da42764c012f743917351dc9a237ea1663610"
+dependencies = [
+ "ring",
+ "rustls-pki-types",
+ "untrusted",
+]
+
 [[package]]
 name = "ryu"
 version = "1.0.17"
@@ -1872,7 +1439,7 @@ version = "2.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "770452e37cad93e0a50d5abc3990d2bc351c36d0328f86cefec2f2fb206eaef6"
 dependencies = [
- "bitflags 1.3.2",
+ "bitflags",
  "core-foundation",
  "core-foundation-sys",
  "libc",
@@ -1965,16 +1532,6 @@ dependencies = [
  "autocfg",
 ]
 
-[[package]]
-name = "socket2"
-version = "0.4.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9f7916fc008ca5542385b89a3d3ce689953c143e9304a9bf8beec1de48994c0d"
-dependencies = [
- "libc",
- "winapi",
-]
-
 [[package]]
 name = "socket2"
 version = "0.5.6"
@@ -2089,7 +1646,7 @@ dependencies = [
  "num_cpus",
  "pin-project-lite",
  "signal-hook-registry",
- "socket2 0.5.6",
+ "socket2",
  "tokio-macros",
  "windows-sys 0.48.0",
 ]
@@ -2111,7 +1668,7 @@ version = "0.24.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c28327cf380ac148141087fbfb9de9d7bd4e84ab5d2c28fbc911d753de8a7081"
 dependencies = [
- "rustls",
+ "rustls 0.21.10",
  "tokio",
 ]
 
@@ -2237,12 +1794,6 @@ version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a183cf7feeba97b4dd1c0d46788634f6221d87fa961b305bed08c851829efcc0"
 
-[[package]]
-name = "value-bag"
-version = "1.8.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "74797339c3b98616c009c7c3eb53a0ce41e85c8ec66bd3db96ed132d20cfdee8"
-
 [[package]]
 name = "version_check"
 version = "0.9.4"
@@ -2255,12 +1806,6 @@ version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5c3082ca00d5a5ef149bb8b555a72ae84c9c59f7250f013ac822ac2e49b19c64"
 
-[[package]]
-name = "waker-fn"
-version = "1.1.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f3c4517f54858c779bbcbf228f4fca63d121bf85fbecb2dc578cdf4a39395690"
-
 [[package]]
 name = "want"
 version = "0.3.1"
@@ -2277,79 +1822,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
 
 [[package]]
-name = "wasm-bindgen"
-version = "0.2.92"
+name = "webpki-roots"
+version = "0.26.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4be2531df63900aeb2bca0daaaddec08491ee64ceecbee5076636a3b026795a8"
+checksum = "b3de34ae270483955a94f4b21bdaaeb83d508bb84a01435f393818edb0012009"
 dependencies = [
- "cfg-if",
- "wasm-bindgen-macro",
-]
-
-[[package]]
-name = "wasm-bindgen-backend"
-version = "0.2.92"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "614d787b966d3989fa7bb98a654e369c762374fd3213d212cfc0251257e747da"
-dependencies = [
- "bumpalo",
- "log",
- "once_cell",
- "proc-macro2",
- "quote",
- "syn",
- "wasm-bindgen-shared",
-]
-
-[[package]]
-name = "wasm-bindgen-futures"
-version = "0.4.42"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "76bc14366121efc8dbb487ab05bcc9d346b3b5ec0eaa76e46594cabbe51762c0"
-dependencies = [
- "cfg-if",
- "js-sys",
- "wasm-bindgen",
- "web-sys",
-]
-
-[[package]]
-name = "wasm-bindgen-macro"
-version = "0.2.92"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a1f8823de937b71b9460c0c34e25f3da88250760bec0ebac694b49997550d726"
-dependencies = [
- "quote",
- "wasm-bindgen-macro-support",
-]
-
-[[package]]
-name = "wasm-bindgen-macro-support"
-version = "0.2.92"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e94f17b526d0a461a191c78ea52bbce64071ed5c04c9ffe424dcb38f74171bb7"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
- "wasm-bindgen-backend",
- "wasm-bindgen-shared",
-]
-
-[[package]]
-name = "wasm-bindgen-shared"
-version = "0.2.92"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af190c94f2773fdb3729c55b007a722abb5384da03bc0986df4c289bf5567e96"
-
-[[package]]
-name = "web-sys"
-version = "0.3.69"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77afa9a11836342370f4817622a2f0f418b134426d91a82dfb48f532d2ec13ef"
-dependencies = [
- "js-sys",
- "wasm-bindgen",
+ "rustls-pki-types",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index c892c24..91a94c8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,4 +12,4 @@ tokio = { version = "1", features = ["macros", "rt-multi-thread"] }
 serde = { version = "1.0", features = ["derive"] }
 toml = { version = "0.5.8" }
 eyre = "0.6.12"
-lettre = { version = "0.11.6", features = ["builder", "sendmail-transport", "tokio1"], default-features = false }
+lettre = { version = "0.11.6", features = ["builder", "smtp-transport", "rustls-tls"], default-features = false }
diff --git a/src/main.rs b/src/main.rs
index 578257f..efda5f1 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,15 +1,45 @@
 use aws_sdk_s3 as s3;
-use eyre::{OptionExt, WrapErr};
+use eyre::{eyre, OptionExt, WrapErr};
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::convert::TryFrom;
-use std::fmt;
+use std::{fmt,env};
 use std::time::{Duration, SystemTime};
 
 const RESTIC_ALARM_BUCKET: &str = "restic-alarm-state";
 const RESTIC_ALARM_STATE_FILE: &str = "state.toml";
 const RESTIC_ALARM_WATCH_DIR: &str = "watch/";
 
+struct SmtpConfig {
+    address: String,
+    username: String,
+    password: String,
+}
+
+impl SmtpConfig {
+    fn mailer(&self) -> Result<lettre::SmtpTransport, lettre::transport::smtp::Error> {
+        use lettre::SmtpTransport;
+        use lettre::transport::smtp::authentication::Credentials;
+        Ok(SmtpTransport::relay(&self.address)?
+           .credentials(Credentials::new(
+               self.username.to_owned(),
+               self.password.to_owned(),
+           ))
+           .build())
+    }
+
+    async fn from_env() -> eyre::Result<SmtpConfig> {
+        let address = env::var("SMTP_ADDRESS")?;
+        let username = env::var("SMTP_USERNAME")?;
+        let password = env::var("SMTP_PASSWORD")?;
+        let smtp = SmtpConfig { address, username, password };
+        if ! smtp.mailer()?.test_connection()? {
+            return Err(eyre!("Unable to contact the SMTP relay"))
+        }
+        Ok(smtp)
+    }
+}
+
 #[derive(Serialize, Deserialize, Clone, Debug)]
 struct State {
     last_alert: HashMap<String, u64>,
@@ -95,12 +125,13 @@ fn is_alert_needed(
 }
 
 async fn send_email(
+    smtp: &SmtpConfig,
     name: &Option<String>,
     email: &str,
     repo: &str,
     inactive: Duration,
 ) -> eyre::Result<()> {
-    use lettre::{AsyncSendmailTransport, AsyncTransport, Message};
+    use lettre::{Message, Transport};
     let email = Message::builder()
         .from("infracoll <root@infracoll>".parse().unwrap())
         .to(email.parse()?)
@@ -117,8 +148,7 @@ async fn send_email(
             inactive.as_secs() / (3600 * 24)
         ))
         .unwrap();
-    let mailer = AsyncSendmailTransport::new();
-    mailer.send(email).await?;
+    smtp.mailer()?.send(&email)?;
     Ok(())
 }
 
@@ -245,7 +275,7 @@ struct RepoInfo {
 // (e.g. if it fails to parse).
 // So the error must not be propagated to the toplevel, which would abort the
 // alert for remaining repositories; it should instead just be reported/logged.
-async fn check_repo(client: &s3::Client, state: &mut State, repo: &str) -> eyre::Result<RepoInfo> {
+async fn check_repo(smtp: &SmtpConfig, client: &s3::Client, state: &mut State, repo: &str) -> eyre::Result<RepoInfo> {
     let config = read_repo_config(client, repo).await?;
     let alert_status = if let Some(inactivity) = repo_last_snapshot(client, repo).await? {
         let last_alert = state.last_alert(repo);
@@ -256,7 +286,7 @@ async fn check_repo(client: &s3::Client, state: &mut State, repo: &str) -> eyre:
                 config.email,
                 repo_name(repo, &config.name)
             );
-            send_email(&config.name, &config.email, repo, inactivity).await?;
+            send_email(smtp, &config.name, &config.email, repo, inactivity).await?;
             state.update_last_alert(repo);
             write_state(client, state).await?;
         }
@@ -281,13 +311,14 @@ async fn main() -> eyre::Result<()> {
         .force_path_style(true)
         .build();
     let client = aws_sdk_s3::Client::from_conf(config);
+    let smtp = SmtpConfig::from_env().await?;
 
     let repos = to_watch(&client).await?;
     println!("Watching {} repos", repos.len());
     let mut state = read_state(&client).await?;
 
     for repo in repos {
-        match check_repo(&client, &mut state, &repo).await {
+        match check_repo(&smtp, &client, &mut state, &repo).await {
             Ok(RepoInfo {
                 name,
                 alert_status: None,