Configure exim to use remote smtp with authentication

Question

I have a dedicated server with exim on it. I also have a regular shared hosting account ("sharedhostingdomain.com") on hostgator. I want to configure exim to always use hostgator's smtp server ("mail.sharedhostingdomain.com") for email delivery.

The problem is that hostgator's smtp server is obviously requiring authentication and it's on a different port (26). Since I do have legitimate account, I do have access credentials, but I don't know how to force exim to always use that SMTP server instead of trying to connect to the receipient's smtp server directly and where to specify those access credentials.

score 3 · Answer 1 · answered Feb 23 '12 at 12:16

As Daniel says, you need to configure exim as a smarthost. This means defining a router like this (N.B. the double colon separating the hostname and the port number):

send_to_smarthost:
  debug_print = "R: smarthost for $local_part@$domain"
  driver = manualroute
  domains = ! +local_domains
  transport = remote_smtp_smarthost
  route_list = * smarthost.example.com::26
  host_find_failed = defer
  no_more

and then a transport that can prod exim into authentication:

remote_smtp_smarthost:
  debug_print = "T: remote_smtp_smarthost for $local_part@$domain"
  driver = smtp
  hosts_require_auth = smarthost.example.com

For a lot of distributions, you can now just put your host:username:password triplet into /etc/exim/passwd.client and this should just work.

I believe that instead of specifying the port in the router, you can use the port command in the transport. In theory, both should work.

score 1 · Answer 2 · edited Jun 11 '20 at 10:02

It's been a while since I've done anything interested with exim configs, but I can give you some basic pointers. This will also depend on which version of exim you are running, and which distro as well (eg, debian has a meta-config configuration file, which abstracts a lot of this for you).

Basically, you'll want to configure exim with a smarthost, set to hostgator's SMTP server. (This used to be called a "router" in exim-talk, I think it still is).

The transport that your router is configured with will need to be told to use port 26, not port 25. (There is a "port" variable you can set)

You'll also need to setup exim client authentication (eg, check here for the bit on "Authentication by an exim client"

Sorry I can't be more specific than that, but hopefully this is enough to get you on your way.

Configure exim to use remote smtp with authentication

2 Answers2