Re: Gnus with Exim

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

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

> Okay, I'm going to ask you "what should I do next to configure Exim
> so that I can send mail from anywhere?"

After thinking it over for a few days, I think I'd take advantage of
some of exim's new configuration file "preprocessor-like" features and
use a swappable smart host setup, skipping the dnslookup stuff.

You could define a router like the "smart_route" one defined in the
first exim.conf I shared, but rather than specifying smtp.rcn.com
directly, use file inclusion to pull in a one- or two-line snippet
from a separate file that defines your current SMTP server. It's only
a slightly less ugly version of the multiple exim.conf file scheme I
mentioned a few days ago, but I think it best captures your
requirements.

Rather than using this directly,

,----
| smart_route:
|   driver = manualroute
|   domains = ! +local_domains
|   transport = remote_smtp
|   route_list = * smtp.rcn.com
`----

you could use this¹:

,----
| smart_route:
|   driver = manualroute
|   domains = ! +local_domains
|   transport = remote_smtp
|   .include /etc/exim_smarthost_route_list
`----

The file /etc/exim_smarthost_route_list could be a symlink that
pointed to one of two files:

,----[ /etc/exim_rcn_route_list ]
| route_list = * smtp.rcn.com
`----

,----[ /etc/exim_bc_route_list ]
| route_list = * smtp.boost-consulting.com
`----

You'd have to flip that symlink each time you changed your computer's
physical location.

Alternately, why not try this first and see if it suits your
needs. Specify multiple servers in your smart host route list, and let
them be tried in order:

,----
| smart_route:
|   driver = manualroute
|   domains = ! +local_domains
|   transport = remote_smtp
|   route_list = * smtp.rcn.com:smtp.boost-consulting.com
`----

The only trouble there arises if one of those servers operates on a
non-standard port, or rather if they operate on different ports. The
SMTP port is specified as part of the remote_smtp transport.² That
means that if the two smart hosts operate on different ports, they
need different remote_smtp transport specifications:

,----
| smart_route:
|   driver = manualroute
|   domains = ! +local_domains
|   transport = remote_smtp
|   route_list = * smtp.rcn.com
|   host_find_failed = pass
|
| smart_route_fallback:
|   driver = manualroute
|   domains = ! +local_domains
|   transport = remote_smtp_special
|   route_list = * smtp.boost-consulting.com
`----

,----[ Transport to handle non-standard SMTP port ]
| remote_smtp_special:
|   driver = smtp
|   port = 2525
`----

I have not tested this configuration -- host_find_failed in particular
-- but it matches my reading of the manualroute router documentation.³


[...]

> I'd be satisfied with a configuration that tried smtp.rcn.com and
> then fell back to smtp.boost-consulting.com.  That scheme seems to
> work in 99% of all locations.

Please consider the proposals above and let me know what you think.


Footnotes: 
¹ http://www.exim.org/exim-html-4.50/doc/html/spec_6.html#SECT6.3
² http://www.exim.org/exim-html-4.50/doc/html/spec_30.html#IX2248
³ http://www.exim.org/exim-html-4.50/doc/html/spec_20.html#IX1733

-- 
Steven E. Harris