Servers like Postfix with Dovecot SASL or Exchange can fail PLAIN with
451 4.3.2 but accept LOGIN. MindSift now uses LOGIN directly when it is
the only mechanism, and otherwise reconnects and retries with LOGIN after
a refused PLAIN (net/smtp closes the connection on a failed AUTH). If both
fail with 451, the error names both attempts and points to the server's
SASL backend. LOGIN, like PLAIN, is never sent unencrypted to remote hosts.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
sandrodachandClaude Opus 5.5
d8a16c6775