Re: Gnus with Exim

["Steven E. Harris" <seh@panix.com>]

David Abrahams <dave@boost-consulting.com> writes:

> Well, actually that's probably enough.  I don't normally have errors;
> it just seems like my emacs session sometimes locks up for up to a
> minute when trying to send mail.

That was my original motivation for setting up exim too. But after
running exim for several years, I have seen sending errors arise where
the queuing and retrying capability turns out to be very convenient. I
run my exim daemon with a queue run interval of 10 minutes. Given that
my queue is usually empty, the daemon does virtually no work. On the
other hand, on the odd chance that a message can't be sent out right
away, I don't have to worry much about attending to it later.

> The only thing that worries me is what happens in the rare case where
> sending *does* actually fail.

Exim will send a message back to the sender (you) when it's ready to
give up on delivery, or if delivery is taking a very long time. To
discuss failure behavior, though, we need to distinguish between
transient failures and permanent failures.

> Actually, I think there's a better answer.  See the enclosed message.
> I just need to figure out how to apply what he says there.  You might
> want to modify your use of &/+ accordingly.

I don't think the intentions are the same. While it is nice that the
fallback_hosts option can accept multiple hosts, you have to go
through the sure-to-fail direct DNS lookup first, wait for that to
fail, and only then start trying the list of obliging servers.

> It's called exim-config on cygwin ;-)

No, the exim4-config package on Debian goes way, way beyond the
exim-config in Cygwin. For my setup at home in Debian, the only
hand-tweaking I had to do was to get my ISP's unusual SMTP server port
specified; at present, despite a few bug reports to the contrary, the
server port is not considered to be an important configurable setting.

> The ideal thing would be to get the fallback stuff working.
> Unfortunately I have to take my computer down the block to test it ;-)

I have the fallback stuff set up on my computer at work ("=" for
"fallback on FAIL only"), but the fallback scenario never gets
triggered. The work setup is different than the one I shared with
you. I can make direct connections to /almost/ any SMTP server out
there, but, paradoxically, I can't send mail to my coworkers by coming
back in to our own SMTP server as pointed to in the public MX
records. So, for internal mail, I use a corporate server as a "smart
host", but for external mail I use the dnslookup driver to connect
directly, and fallback on FAIL to our internal "smart host".

> Oh, well *that* might be a better option.  I could get the guy who
> administers smtp.boost-consulting.com to open a different port for
> outgoing SMTP so I can send email that way.

That will work in environments that block port 25, and that do /not/
block all ports besides, say, HTTP and HTTPS. Panix runs on port
2525¹. I have yet to find that port blocked anywhere I use my computer.

> Then I wouldn't need exim at all, would I?

I would still recommend running it. It solves problems that your MUA
alone doesn't solve. You started out this inquiry looking for
asynchronous sending behavior from Gnus, and getting that extra SMTP
port opened won't grant you that behavior. It will make configuring
exim to fit your roaming scenario easier.

> In fact, I could probably test this by going through smtp.panix.com
> if you tell me what port you're using.

It's mail.panix.com on port 2525, but you'll need to authenticate if
you're not coming in through a Panix connection.

[...]

> Maybe the enclosed will help.

Oh, I see they changed the "+ for DEFER or FAIL" to "&".

[...]

>> bash-2.05b$ telnet smtp.boost-consulting.com 25
>> Connecting To smtp.boost-consulting.com...
>> <long delay here>
>> Connecting To smtp.boost-consulting.com...Could not open connection to the
> host, on port 25: Connect
>>  failed
>> bash-2.05b$
>>
>> > Does it intercept the call and return an error (failure outcome), or
>> > does it let you hang until you time-out (defer outcome)?
>>
>> I think this is defer outcome, yes?
>
> Yes.
>
>> Can I set up exim to fallback on defer?  This is what I have now:

It looks to me as though your ISP is blocking port 25 traffic, so it
doesn't make sense to even try using the dnslookup router when you're
stuck behind this connection. The "smart host" one is a short-circuit
pessimistic version of your dnslookup+fallback: Don't even bother
trying to connect directly, and just send it out through smtp.rcn.com.


Footnotes: 
¹ http://www.panix.com/panix/help/mail.smtp-outside.html

-- 
Steven E. Harris