We're having an issue right now with certain users replying to emails (the reply does go through) but their sender email address has changed and appended the send domain to it.
It would normally look like: email@example.com But it's been changed to: firstname.lastname@example.org
This causes issues when someone tries to respond back to that reply, as it will no longer go back to the user (because the email address does not exist on our domain). Any idea why this might be happening? Is this an issue with our reply mail management?