Marc Sherman wrote: > Heiko Schlittermann wrote: > >> Anyway - what about implementing the fallback_hosts feature not for >> temporary errors but for 5xx errors too? >> >> The rationale: There's a mail server sending from non-rDNS-able address. >> On most connections it works, but some reject this server with 5xx. In >> this, *only* this case I'd like to route the mails to some friendly >> smarthost... >> >> (The smart host uses callout for recipient checks, so if the 5xx is >> because of some other reason, it should reject the mail at SMTP time >> already, thus refusing its smart service.) >> >> Could please somebody explain me, why it's a stupid idea? ;-) >> > > This has been discussed ad nauseam many times in the past. It will _not_ > give you a reliable mail server even if implemented. A large number of > sites do not reject blacklisted messages with 550's, but rather > quarantine or blackhole them. So implementing this feature will have all > the negatives of violating the RFCs, and none of the intended benefits. > > http://www.google.ca/search?q=site:www.exim.org/mail-archives+fallback+OR+retry+smarthost&hl=en&lr=&start=10&sa=N > > - Marc > >
Picture this situation. I have several IPs to send mail on to forward to my customers. One transport uses IP address A and for some unknown reason A becomes accidentally blacklisted. So the customers hosting company starts bouncing all the email coming from my filtering service for that customer. But - if it could be passed on to another transport that sends on a different IP then it would perhaps go through. As I have said. Would never do this for all outgoing email but only in very targeted situations. -- ## List details at http://www.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://www.exim.org/eximwiki/
