I have Mailcow setup with Address Rewriting > BCC Maps to forward all incoming mail from Mailcow to my personal Gmail account. This worked fine for a week or so, then I had someone mention that their own mail server was bouncing messages when replying to my emails. Note that they were replying to my custom domain email hosted on Mailcow, but somehow, their bounce emails were from Gmail that contained my personal Gmail address which shouldn’t be publicly seen.
I have the BCC map setup like so:
local destination: firstname.lastname@example.org
bcc destination: email@example.com
bcc type: recipient map
Any idea why my personal gmail is being used when someone replies to an email with the Mailcow BCC map setup?