How to set up a smarthost to follow max hourly mail limits

Introduction

If your server uses a smarthost for sending mail, and you want Exim to follow the maximum hourly email-sending limits, you must configure Exim as outlined here.

Procedure

In WHM, navigate to the Advanced Editor of the Exim Configuration Manager. For each of the referenced sections, enter the information below that section into the corresponding boxes in the configuration editor.

Section: POSTMAILCOUNT

The POSTMAILCOUNT section must be used instead of ROUTERSTART for max hourly mail limits to be followed and used. You must also add the domains = section section if you want the server to still accept mail for local domains and only relay mail out; otherwise, all email--incoming and outgoing--gets relayed through the smarthost. Also, make sure to replace smtp.server.com with your smarthost's hostname:

remoteserver_route:
  driver = manualroute
  transport = remoteserver_relay
  domains = !+local_domains
  route_list = * smtp.server.com

Section: TRANSPORTSTART

Make sure to update $host_address with your smarthost's IP address:

remoteserver_relay:
  driver = smtp
  port = 587
  hosts_require_auth = $host_address
  hosts_require_tls = $host_address

Section: AUTH

Make sure to update this information with your smarthost's username and password:

remoteserver_login:
  driver = plaintext
  public_name = LOGIN
  hide client_send = : user@domain.com : password

DKIM

If you also want to use DKIM, add the following to each section:

Section: POSTMAILCOUNT

smarthost_dkim:
  driver = manualroute
  domains = !+local_domains
  require_files = "+/var/cpanel/domain_keys/private/${sender_address_domain}"
  transport = remote_smtp_smart_dkim
  route_list = * smtp.domain.com

Section: TRANSPORTSTART

remote_smtp_smart_dkim:
  driver = smtp
  hosts_require_tls = *
  interface = ${if exists {/etc/mailips}{${lookup{$sender_address_domain}lsearch*{/etc/mailips}{$value}{}}}{}}
  helo_data = ${if exists {/etc/mailhelo}{${lookup{$sender_address_domain}lsearch*{/etc/mailhelo}{$value}{$primary_hostname}}}{$primary_hostname}}
  dkim_domain = $sender_address_domain
  dkim_selector = default
  dkim_private_key = "/var/cpanel/domain_keys/private/${dkim_domain}"
  dkim_canon = relaxed

Once you have finished adding the above information to all the appropriate sections, navigate to the bottom of the page and select Save. This automatically applies the settings and restarts Exim. Now any email sent out will be routed through the remote smarthost and will follow the max hourly mail limits.