On Hosted CanIt, you may see logs similar to this:
5.1.8 <firstname.lastname@example.org>... Domain of sender address email@example.com does not exist
Hosted CanIt always rejects messages where the domain of the envelope sender (in the example above,
pqrst.example.com lacks an A or an MX record. This policy is absolutely firm.
Why do we reject unresolvable domains?
If there is a delivery problem, the Internet standards require that a failure
notification be sent to the envelope sender (in this example,
firstname.lastname@example.org). If that domain does not exist, then obviously no failure notification can be sent.
How can I make this work?
Only the sender of the email can fix the problem. There are several options available:
- Make sure the domain of the envelope sender address is resolvable. That is, whatever comes after the
@sign in the sender address must have an A record, an MX record, or both.
- Use the null return path
<>as the envelope sender. This is useful for situations in which you don't care to receive failure notifications.
If you use an on-site implementation of CanIt, you can work around this by explicitly allowing mail from that hostname as described here. This should NOT be considered a solution and Roaring Penguin will absolutely NOT do this for Hosted CanIt.
But won't Roaring Penguin please make an exception and allow an unresolvable domain through?
No, sorry. It is an error to send mail from unresolvable domains and the onus is on the sender to fix the problem.