- UseTLS now tries implicit TLS first (port 465 semantics) and, when the
server answers in plaintext (tls.RecordHeaderError, e.g. port 587
submission), automatically retries with mandatory STARTTLS; encryption
is never silently downgraded (fixes#1470, supersedes #1488)
- TestSMTPConnectionWithConfig now shares connectSMTP with the send path,
adding the opportunistic STARTTLS upgrade the send path gained in
b402c367d; this removes the 'test connection fails but test email
sends' mismatch reported in #1488
- test-connection now also honors dial/IO timeouts and ignores
non-standard QUIT responses, matching the send path
shaw
4c80d160dd