Mario Fetka
1.2 KiB
SMTP extensions
Bongo keeps the classic HELO/MAIL/RCPT/DATA path for old clients and
advertises ESMTP extensions after EHLO. The server advertises 8BITMIME and
SMTPUTF8 only when the corresponding configuration is enabled. SMTPUTF8
is accepted as a MAIL FROM parameter only after EHLO; non-ASCII envelope
addresses require it and are validated as UTF-8.
BODY=8BITMIME is recorded with the queued message and is sent to a remote
peer only when that peer advertises 8BITMIME. Bongo does not implement
BDAT/CHUNKING, so BODY=BINARYMIME is rejected explicitly instead of
silently treating binary data as a normal DATA message.
Outgoing SMTP uses the peer's advertised SIZE, 8BITMIME and SMTPUTF8
capabilities. Internationalized domains are converted to their DNS
ASCII-compatible form for MX lookup while the original UTF-8 address remains
in the SMTP envelope. External SMTP relays use libcurl and receive the same
SMTPUTF8/BODY=8BITMIME envelope parameters.