On Mon, Sep 09, 2013 at 12:30:43PM -0400, Roman Gelfand wrote: > It appears that by default if target domain can't be dns > resolved, there is a local hard bounce.
Depends. Was it a temporary DNS failure: SERVFAIL or timeout? Or, rather, was it a permanent error like NXDOMAIN? Also, this does not have to happen if you check the recipient address/domain before accepting the mail. See access(5) and postconf.5.html#reject_unknown_recipient_domain . I usually use reject_unknown_recipient_domain on submission. Some sites might not want this. > What setting controls the bounce behavior? See postconf.5.html#unknown_address_reject_code > At the same time, if the target mail server is not available, the > delivery is going to be deferred by default. > > Does postfix recognize the difference between local firewall > blocking access to target server as opposed to target mail > server not available? No; I cannot imagine how Postfix might be able to determine the causes of network failures. All it can know and report is that the network connection failed. > dns server not resolving and dns server not available? See above regarding various DNS responses, and if interested, read more on the DNS protocol. Wikipedia might be a good start. -- http://rob0.nodns4.us/ -- system administration and consulting Offlist GMX mail is seen only if "/dev/rob0" is in the Subject:
