Exim SMTP Smarthost Setup

eximsmarthostsmtp

I used these settings to set up exim to use gmail as a smarthost, which worked. However, I don't seem to be able to use these settings against other smtp servers, such as Yahoo or Fastmail (both with port 465 instead of 587). Both of these fail with the message defer (-18): Remote host smtp.example.com [x.x.x.x] closed connection in response to initial connection. Is there anything wrong with these settings? What could be going wrong?

my_route:
  driver = manualroute
  domains = ! +local_domains
  transport = my_relay
  route_list = * smtp.mail.yahoo.com

my_relay:
  driver = smtp
  port = 465
  hosts_require_auth = $host_address
  hosts_require_tls = $host_address

my_login:
  driver = plaintext
  public_name = LOGIN
  hide client_send = : my_username@yahoo.com : my_password

Best Answer

Had same challenge and solved it by changing smtp port from 465 (SSL/TLS) to 587 (STARTTLS).

Related Solutions

SMTP smarthost round-robin balancing

Your provider's an idiot. They should give you one server name to plug into your MTA and do their own load balancing. I'd be inclined just to throw one name into my relayhost directive and be done with it. You could define a local name with the A records of all your provider's machines (taken from resolving the names they've given you), but it makes no sense to have to do so, because every time your provider decides to add more servers to their cluster you have to make a config change.

Exim4 smarthost with sender verification

In effect, you're setting up a front-end MX with a more restrictive set of filters deeper towards the final destination. The best way to tackle this is to be at least as restrictive at the front-end.

Because you have a smarthost though, you send email for "any domain" out to the smarthost. This combines badly with domain validity checking: somewhere in your ACL defined for RCPT commands, there should be a require verify = sender which ensures that Exim has a method for sending email to the sender domain before it will accept the message.

Since you're always-on, I recommend putting an extra Router directly before your smarthost Router. Assuming that the smarthost has domains = ! +local_domains and no_more, then add no_verify to the smarthost Router and before it, insert this Router:

remote_dns_verify:
  driver = dnslookup
  domains = ! +local_domains
  transport = remote_smtp
  # ignore_target_hosts = +some_hostlist_matching_rfc1918_and_so_on
  same_domain_copy_routing
  verify_only
  no_more

With this, the verification path will not use the smarthost, so you will no longer have "a route for everything". The verification will only be able to route remote domains which have DNS, so you'll no longer accept emails which your ISP is rejecting for being unrouteable.

After that, I'd look into setting some retry rules which match specific remote errors to stop retrying mails which the ISP has rejected. See http://www.exim.org/exim-html-current/doc/html/spec_html/ch-retry_configuration.html for more.

Best Answer

Related Solutions

SMTP smarthost round-robin balancing

Exim4 smarthost with sender verification

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