Investigate the shape of an 'inbound' email sending class

[brendanheywood]

eg this affects the way the sender headers get written on outbound emails

This will be a core tracker

[bwalkerl]

When $CFG->handlebounces is enabled, core does set $mail->Sender = generate_email_processing_address(0, $modargs);

This is showing up in the logs on bounces as the send address (i.e. something like mdlAABAgAABA==91b4ee34a1a3e9c2068552cc977aafb7@example.com), but from what I've seen this isn't making it to the inbound email headers.

This would usually appear in the Return Path, but it seems to be getting replaced somewhere in the chain (most likely by SES) and ending up as 010301433b1eb9ce-9b9edeee-56bb-4c54-86ba-63f45d0e0cfd-000000@example.com. This happens regardless of whether the Sender is the handlebounces address or noreply.

Were there any other headers of concern?

[brendanheywood]

This is good enough for right now, as we are not breaking anything when the inbounce system is not configured. We'll come back to this when we tackle the inbound emails