On Tue, 14 Apr 1998, Joe Saladino wrote:
> I have compiled the latest version of exim and was doing some testing
of addresses. It appears that it only checks the domain name and not
the actual user.
For remove domains, yes.
> My question is, can I use some kind of filter that would chat with the
remote mailserver and stop short of actually sending an e-mail message?
In other words I could do a echo "test"|exim -v <address> and when the
remote host says something like unknown user then return with an error
code that I could use in a program and if it says User OK or something
like that, stop immediately and cancel the transmission of the message
to the remote server.
(1) This has been suggested before. Personally, I don't think it would be
all that useful because it would work only if you connect to the final
mailserver *and* it is the sort that allows VRFY *and* it does a genuine
verification. Some mailers accept any local part and give an error
afterwards (aol.com is like this) and it might be that they apply the
same rules to VRFY, i.e. just do a plausibility/syntax/domain check.
Actually, they don't allow VRFY:
220-relay13.mx.aol.com ESMTP Sendmail 8.8.5/8.8.5/AOL-4.0.0; Wed, 15 Apr
1998 04:44:39 -0400 (EDT)
220-America Online (AOL) does not authorize the use of its proprietary
220-computers and computer network to accept, transmit or distribute
220 unsolicited bulk e-mail sent from the Internet.
vrfy postmaster@???
252 Cannot VRFY user; try RCPT to attempt delivery (or try finger)
and testing with RCPT TO is useless, because they accept anything.
(2) Backup mailservers, hubs, and gateways are common. Many of them
don't (can't) check local parts. If Exim connected to one of them, the
test wouldn't be helpful. You would also be likely to get a lot of
"temporary" failures of various kinds.
(3) Connections to hosts in some parts of the Internet are extremely slow.
This could add quite a lot of extra load/delay on such connections.
and, on a practical point, this would require a fair bit of messing with
the code, which I'm not very keen on either.
--
Philip Hazel University Computing Service,
ph10@??? New Museums Site, Cambridge CB2 3QG,
P.Hazel@??? England. Phone: +44 1223 334714
--
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