DKIM signature is missing

I use Mautic as an email client on mautic.qqq.qq domain and Axigen as an smtp server on mail.qqq.qq domain.
Emails are sent from Mautic and it is OK.

I can not set up Axigen to DKIM sign messages which are originated by Mautic.
If I send it from WebMail they are DKIM signed.

What would you suggest?