Dickenson, Steven wrote:
> Hi guys,
> Using Marc Merlin's Debian package for Exim v4.10 w/ SA-Exim.
>
> I have a sender verify acl in check_rcpt that looks like this...
>
> deny hosts = !+localadds:!+host_disable_callback:*
> sender_domains = !+envdomain_disable_callback:*
> local_parts = !+noenvfromcallback
> !verify = sender/callout=90s/check_postmaster
>
> Can someone tell me exactly what check_postmaster does? I can't
> find it in the Exim docs, and search of the list archives turns up nothing,
> except excerpts from Marc's configuration file.
>
> I assume it checks for the existence of a postmaster account during
> sender verification. Can I do sender verification without this? We
> communicate with a number of independent schools that are typically
> understaffed, and have poorly managed/designed networks. Thus, they usually
> run MS Exchange and don't have a postmaster account.
check_postmaster first appeared in exim 4.12 (maybe marc added one of
the earlier patches?), but you can remove the option if you want.
from exim4.12 doc/NewStuff:
<quote>
3. There is a new option called check_postmaster that can be used whenever
a callout option is set on an address verification in an ACL. For
example:
accept verify = sender/callout/check_postmaster
This causes Exim to do a double check. After it has verified the
address in
an SMTP connection, it also verifies that the same server will
accept mail
to "postmaster" at the same domain, within the same SMTP connection. If
postmaster is rejected, the verify condition fails.
</quote>
Servers without a postmaster-account are broken (RFC2821):
<quote>
Any system that includes an SMTP server supporting mail relaying or
delivery MUST support the reserved mailbox "postmaster" as a case-
insensitive local name. This postmaster address is not strictly
necessary if the server always returns 554 on connection opening (as
described in section 3.1). The requirement to accept mail for
postmaster implies that RCPT commands which specify a mailbox for
postmaster at any of the domains for which the SMTP server provides
mail service, as well as the special case of "RCPT TO:<Postmaster>"
(with no domain specification), MUST be supported.
</quote>
Nico
