Re: Gnus with Exim

[David Abrahams <dave@boost-consulting.com>]

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"Steven E. Harris" <seh@panix.com> writes:

> David Abrahams <dave@boost-consulting.com> writes:
>
>> It's working!  This is fantastic, thank you!
>
> Great news.
>
>> A few more questions
>>
>> 1. I allowed exim-config to start it as a service:
>
> [...]
>
>>    I figured that's what I needed to do in order to get the
>>    asynchronous sending behavior I'm after (remember that my SMTP
>>    server is not responsive enough for me).  Is that right, or is
>>    there a way to do this that only causes exim to run
>>    (asynchronously) when it's time to actually send something?
>
> I assume you mean that no service runs until it's time to send a
> message? Exim will work fine that way, but the problem comes right
> back around to your raison d'etre for setting up exim in the first
> place: When a sending attempt fails, the message will be queued, but
> there will be no automatic retrying and dispatching of that
> queue.
>
> That is, you are free to call on exim at any time to send an outbound
> message, but if that first attempt fails you may be on your own for
> triggering exim to try again later. Some experimentation may reveal
> that the /next/ time exim tries to send another message, it will also
> process any other pending messages in the queue. I'm not sure about
> that.

Hmm.  

> One thing that does seem helpful, observable through casual
> experimentation, is that even when exim is invoked to accept an
> outbound message with no daemon running, it accepts and sends the
> message with two different processes, so the calling program doesn't
> block through the sending attempt.

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.

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

>> 2. Of course, my ISP not only insists that I use their SMTP server
>>    when I'm at home, but their server refuses to respond when I'm
>>    away.  So I have to use smtp.boost-consulting.com.  I don't want to
>>    edit my exim-config and restart the daemon in those cases if
>>    possible.  Any ideas?
>
> I used to have this problem, and my solution was barely mentionable: I
> had a script that flipped the permissions on exim.conf, swapped a
> symlink to one of three nearly-identical configuration files, and
> restored the permissions. I could have ran sed or similar over the
> file to swap the server names, but I didn't like seeing the
> modification times change on the file(s).

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.

> Debian has a system wherein the actual exim.conf file is generated
> from a separate set of settings and small template files. With that
> arrangement, it would be possible to change the server setting and
> regenerate the file. Again, though, that's a hack.

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

> Exim does have all sorts of read-and-search-this-file-or-database
> capabilities. Debian uses it for the /etc/email-addresses lookup, and
> also to plug in the user name and password for SMTP AUTH/TLS, instead
> of the in-line specification I showed you. Perhaps we could figure out
> how to get exim to read the smart host server from a separate file,
> and you could just change that separate file when your computer
> roams. If you're interested in pursuing this idea, I can help with the
> research.

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

> When I mentioned that I "used to" have this problem, I only "solved"
> it by discovering that my ISP (Panix) runs its SMTP server on several
> alternate ports. That allows me to use the Panix server at home with
> my cable modem despite SMTP being blocked, and to use it when out in a
> cafe or library because again the alternate SMTP port isn't usually
> blocked.

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.  Then I wouldn't need exim
at all, would I?  In fact, I could probably test this by going through
smtp.panix.com if you tell me what port you're using.

>> 3. My IMAP server is not super fast either.  It's running Exim too,
>>    coincidentally.  Ideally I'd like to set up a mirror of my IMAP
>>    server on a local Linux machine so I can search messages more
>>    quickly and have redundant message storage.  Do you happen to know
>>    of a means to that end?  I imagine this isn't something people want
>>    to do every day.
>
> I have never attempted this, but I'd imagine it would involve having
> something like fetchmail poll your ISP's mail server, download local
> copies of the messages to the IMAP server, while leaving the messages
> on the ISP's server. However, that would not handle the problem of
> synchronizing message deletion, copies, moves, and flag
> alteration. Suddenly the problem gets much harder.

Yep.

>> Thanks again for all your help.
>
> No problem. I've been a casual exim tinkerer for a while now, and
> always enjoy the chance (or the excuse) to learn a little more about
> it.

Maybe the enclosed will help.


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From: "Pierre A. Humblet" <Pierre.Humblet@ieee.org>
To: "David Abrahams" <dave@boost-consulting.com>
Subject: Re: Can't get Exim to send mail
Date: Mon, 06 Jun 2005 11:58:57 -0400
Message-ID: <099901c56ab0$a610e2c0$3e0010ac@wirelessworld.airvananet.com>


----- Original Message ----- 
From: "David Abrahams" <dave@boost-consulting.com>
To: "Pierre A. Humblet" <Pierre.Humblet@ieee.org>
Sent: Monday, June 06, 2005 11:48 AM
Subject: Re: Can't get Exim to send mail


> "Pierre A. Humblet" <Pierre.Humblet@ieee.org> writes:
>
> > It's possible to have several fallbacks, trying them sequentially.
> > I have never tried that together with the special Cygwin patch to allow
> > fallback on failure (native exim only fallbacks on defer).
> > People have suggested making the fallback_host dependent on where
> > you are, but doing that reliably is a non-trivial change.
> > What does your ISP do when you try to connect directly to the
> > destination?
>
> I suppose you mean, e.g. this:
>
> 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:
>
> dnslookup:
>   driver = dnslookup
>   domains = ! +local_domains
>   transport = remote_smtp
>   ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
> # If the first host starts with '&', fallback on DEFER or FAIL.
> # If the first host starts with '=', fallback on FAIL only.
> # If neither, fallback on DEFER only.
> # The first cases are Cygwin extensions for users with dynamic ip
addresses.
>   fallback_hosts = + : smtp.rcn.com
>   no_more

According to your telnet experiment, you want to fallback on DEFER,
but just in case things change, you might as well defer on FAIL.
So I would use a "&".
I don't think a + is appropriate there. Native exim interprets it literally,
trying to fallback to host "+". But with the Cygwin patch, it's interpreted
(or was interpreted) as a "&" (for historical reasons).
It's always interesting to do a
exim -d xxxx@smtp.boost-consulting.com as explained in an earlier
e-mail, to really see what's going on.
Let me know how it goes.

Pierre



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-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com