In DNS, I have service.example.com. CNAME box.example.com.
When sending email automatically to about 10,000 adresses (no worries, nothing sinister), I set envelope-from to [email protected]
. Of the bounces that come back, about 70% have envelope-to set to [email protected]
(which is what I would expect), but about 30% have envelope-to to [email protected]
.
What is going on here? Do some MTAs change envelope-to when they discover a CNAME? Which MTAs?
Is it a good idea to use an A record instead of a CNAME for service.example.com.
?