On Sunday 21 September 2003 15:00, Dean Anderson wrote:
It never sends the email in either case. In the first case, it will say no
such host, and return an error to the user. In the second case, it will
attempt to connect to 64.94.110.11 and will get an error, which will be
returned to the MUA.
In both cases, it is permissible for the MTA to try again later in the
first case.
Both of these are perfectly valid responses. You get them at the same
time, or you get the second one sooner.
Not quite totally true. In the second case - it _will_ connect and initiate
the transfer (helo, mail from, rcpt to) phase of _sending_ the message. It
will fail, but it will make the attempt. Whereas with the first case it will
never try. The second is much, much slower from the perspective of a mail
server.
--
Larry Smith
SysAd ECSIS.NET
sysad(_at_)ecsis(_dot_)net