I am not sure I fully understand the scenario you are describing. Things to keep in mind about the current Exim configuration:
The sent email counting happens before Exim routes the email (expands the forwarders).
It is possible to use up the sent email limit if email is sent from
[email protected] to
[email protected], [email protected], [email protected], ... In other words if instead of writing an email to the forwarder address the sender would instead add multiple recipients in the
To: field.
The send limit could be drained in the following scenario:
User
[email protected] writes an email:
This first email arriving from external host does not count into any send limits. However when
[email protected] hits
Reply To All button on his email client, he sends the following email:
Such email would increase the john mailbox send limit by 4, because he sent an email to 4 recipients.
The local send exemption flag I was planning to add would not help in mixed local/external recipients scenario. The flag for disabling local sends would look like this:
Code:
APPLY_SEND_LIMIT = ${if forany{$recipients_list} { !match_domain{${domain:$item}}{+local_domains} }}
This Exim config blob could be translated as - count sent emails as usual if at least one of the recipients domain is not managed by this server.
This would mean the example above would still bump the mailbox
[email protected] by 4 because one of the recipients is external.
Another thing to keep in mind. The main reason for counting local-to-local sends is to make sure if a company A and company B happens to be using the same server, the emails between them would be properly counted.
It seems too me that you are more interested in not counting the emails from same domain to same domain, not emails from same server to same server (different domains). The old Exim behaviour was to not count emails to the same server.
