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Add discovery support for SMTP with implicit TLS

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Simon Ser 2020-02-19 09:43:01 +01:00
parent 75122a175a
commit bfb2d8a4de
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GPG key ID: 0FDE7BE0E88F5E48
1 changed files with 15 additions and 5 deletions
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20
discover.go
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@ -53,14 +53,24 @@ func discoverIMAP(domain string) (*url.URL, error) {
} }
// discoverSMTP performs a DNS-based SMTP submission service discovery, as // discoverSMTP performs a DNS-based SMTP submission service discovery, as
// defined in RFC 6186 section 3.1. // defined in RFC 6186 section 3.1. RFC 8314 section 5.1 adds a new service for
// SMTP submission with implicit TLS.
func discoverSMTP(domain string) (*url.URL, error) { func discoverSMTP(domain string) (*url.URL, error) {
host, err := discoverTCP("submission", domain) smtpsHost, err := discoverTCP("submissions", domain)
if err != nil { if err != nil {
return nil, err return nil, err
} }
if host == "" { if smtpsHost != "" {
return nil, fmt.Errorf("SMTP service discovery not configured for domain %q", domain) return &url.URL{Scheme: "smtps", Host: smtpsHost}, nil
} }
return &url.URL{Scheme: "smtp", Host: host}, nil
smtpHost, err := discoverTCP("submission", domain)
if err != nil {
return nil, err
}
if smtpHost != "" {
return &url.URL{Scheme: "smtp", Host: smtpHost}, nil
}
return nil, fmt.Errorf("SMTP service discovery not configured for domain %q", domain)
} }