On 3/17/21 9:37 PM, Sam Varshavchik wrote:
> I believe that the generally good track record of historical
> interoperability of SMTP implementations goes back to what's in
> section 4.5.3 of RFC 821, that gives the minimal limits of various
> things, like line lengths. And, incidentally, the minimum number of
> recipients that an SMTP server should accept is 100 recipients.
It's been a long time but I'm pretty sure I've seen situations in which
it made sense for the recipient limit to be 1. For example: a
special-purpose device (e.g. email to fax, email to printer) or a
gateway to a dissimilar mail system, or anything for which it makes
sense to insist that per-recipient errors get immediately reported to
Some do this, others accept any number of RCPT TOs and ignore them all. It
depends on whether the the RCPT TO actually contains any information.
This reminds me that this specification needs to cover message submission. Will
ietf-smtp mailing list