email routing to seemingly un-routeable domains

[/dev/rob0]

On Monday 2005-September-05 15:26, Jim Pazarena wrote:
> SHOULD a mail transport agent accept an email addressed to this
> domain? with no "A" or "MX"

"Should" is a determination of local policy. Some may choose to accept 
submission from local and authenticated clients, then queue and attempt 
delivery, and finally send a bounce. Others might choose to reject. 
Here's what mine does:

...
> rcpt to: <dfsgkjfgsfdgdfsg at sk.sympatico.ca>
< 450 4.1.2 <dfsgkjfgsfdgdfsg at sk.sympatico.ca>: Recipient address
  rejected: Domain not found
...

Neither approach is completely correct for all situations.

> how would it determine how to route it ?

SMTP routing without MX nor A records can only be done with manual 
settings in the MTA. In Postfix terms that would be transport(5) and 
the transport_maps setting. In qmail terms that would be smtproutes(5). 
In BIND terms this would all be off topic. :)
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