Cron Mailer – What Mailer Does Cron Use to Send Mail?

In the routers section of your exim config, you'll have a router that looks something like this:

 lookuphost:
    driver = lookuphost
    transport = remote_smtp

This is what tells exim to deliver mail directly. You need to tell it to use the smarthost instead.

Replace the above router with something like this:

 smarthost:
   driver = manualroute
   domains= ! +local_domains
   transport = remote_smtp 
   route_list = *  smtp.ultrahosting.com  byname
   host_find_failed = defer
   no_more

Make sure that the transport name in the new router is the same as in the original (remote_smtp in this example).

Also, you'll need to restart exim after making these changes.

You could give nail a try. It allows you to specify an attachment.

In your script that generates these files you'd do something like the snippet below to deliver the file as an attachment to an email.

echo "body" | nail -s subject -a example-filename.txt you@example.com