Configuring DKIM

DKIM configuration is available in MailSuite Pro. You'll need to generate DKIM keys, one of the services which can do that for you is:

https://tools.socketlabs.com/dkim/generator

You will need to supply the keys in DNS TXT record of your domain, and in Exim configuration file /etc/exim4/exim4.conf:

DKIM_FILE                       = /opt/afterlogic/etc/ssl-certs/dk.key
DKIM_PRIVATE_KEY                = ${if exists{DKIM_FILE}{DKIM_FILE}{0}}
DKIM_DOMAIN = ${lc:${domain:$h_from:}}
remote_smtp:
    driver = smtp
    dkim_domain           = DKIM_DOMAIN
    dkim_selector         = mail
    dkim_private_key      = DKIM_PRIVATE_KEY
    user = afterlogic
    group = afterlogic
    interface = xx.xx.xx.xx

Most of those lines are already there but they're commented out, be sure to uncomment those and specify selector (mail in the sample, can be anything else) and the proper external IP.

/opt/afterlogic/etc/ssl-certs/dk.key is the file where DKIM key needs to be saved, by default the file isn't there so you need to create it.

If you have multiple domains, create DKIM for one of them, and then supply the same DNS TXT record for all the other domains involved.