[exim] 4095 characters in "To" field limit

Hi,

We're running Exim 4.41 and apparently came accross an issue after years without problem.

It all started when users noticed that the Subject Field was empty when receiving some emails sent to the whole enterprise.

We found out that those emails were received by exim in a way that only the first 4095 characters were available and the Subject field was right after it, as if it missed a carrier return.

It looks like it:

User1 <user1@???>, User2 <user2@domaSubject: Hello World

All emails are sent to several recipients (100+) from Thunderbird. However, emails sent to the same 100+ recipients through another non-Exim SMTP server went through as expected.

Is there something we can do to fix it?

Thank you very much,

Francois