Exim: Restrict Authenticated Outgoing Email with Sender Domain
Most of the outgoing SMTP server allowed the user to set different sender email address once it is authenticated. But we might be in risk for allowing the user to send outgoing bulk/spam email via authenticated SMTP with different sender email address.
In Exim mail MTA, it can restricts at the SMTP authenticated transport.
accept authenticated = * sender_domains = < the_domain_name_1 > : < the_domain_name_2 > control = submission control = dkim_disable_verify
Usually local_domains is the list of the domain hosted on Exim mail server, it can be configured as below too.
accept authenticated = * sender_domains = +local_domains control = submission control = dkim_disable_verify