relayhost question
in [Postfix]
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From: "P.A" on 12 Aug 2010 10:43 Hi, hoping someone can help. I have a situation that I want to send all outgoing mail to 3 servers that are part of a spam cluster which will check the email for spam and deliver it. I was thinking of creating a host in DNS, for example smtp-relay and have it point to 3 different ip addresses that correspond to the 3 spam cluster servers. Will this create an issue if postfix does a dns lookup for smtp-relay and gets an ip that is down, will it try again, or is it best to just use all 3 servers names in the relayhost option? Another question is, suppose all three servers are down, can I have postfix directly deliver the email if all relayhosts are down, how can I do this? Sorry if this has been answered I looked and couldn't find it. Thanks, Paul
From: Noel Jones on 12 Aug 2010 11:01 On 8/12/2010 9:43 AM, P.A wrote: > Hi, hoping someone can help. > > I have a situation that I want to send all outgoing mail to 3 > servers that are part of a spam cluster which will check the > email for spam and deliver it. > > I was thinking of creating a host in DNS, for example > smtp-relay and have it point to 3 different ip addresses that > correspond to the 3 spam cluster servers. Yes, this is the proper procedure. > Will this create an > issue if postfix does a dns lookup for smtp-relay and gets an > ip that is down, will it try again, If one is down, postfix will use the others. If all are down, postfix will retry delivery for maximal_queue_lifetime (default 5 days). > or is it best to just use > all 3 servers names in the relayhost option? No, only one relayhost destination may be specified. http://www.postfix.org/postconf.5.html#relayhost > Another question is, suppose all three servers are down, can I > have postfix directly deliver the email if all relayhosts are > down, how can I do this? You can remove the relayhost setting and reload postfix. Postfix won't do this automatically, but you could use a monitoring script of some type. Before you do this ask yourself the question of why use a relayhost at all if you don't mind delivering the mail directly. -- Noel Jones
From: "P.A" on 12 Aug 2010 11:11 Noel, thanks for the quick reply. I don't mind delivering directly if all the relayhosts are down, because it's better than the email sitting in the queue waiting. The only reason I want the email to be forward is so it can be checked for spam. I think this would be a good feature for future versions of postfix. Paul. -----Original Message----- From: owner-postfix-users(a)postfix.org [mailto:owner-postfix-users(a)postfix.org] On Behalf Of Noel Jones Sent: Thursday, August 12, 2010 11:01 AM To: postfix-users(a)postfix.org Subject: Re: relayhost question On 8/12/2010 9:43 AM, P.A wrote: > Hi, hoping someone can help. > > I have a situation that I want to send all outgoing mail to 3 > servers that are part of a spam cluster which will check the > email for spam and deliver it. > > I was thinking of creating a host in DNS, for example > smtp-relay and have it point to 3 different ip addresses that > correspond to the 3 spam cluster servers. Yes, this is the proper procedure. > Will this create an > issue if postfix does a dns lookup for smtp-relay and gets an > ip that is down, will it try again, If one is down, postfix will use the others. If all are down, postfix will retry delivery for maximal_queue_lifetime (default 5 days). > or is it best to just use > all 3 servers names in the relayhost option? No, only one relayhost destination may be specified. http://www.postfix.org/postconf.5.html#relayhost > Another question is, suppose all three servers are down, can I > have postfix directly deliver the email if all relayhosts are > down, how can I do this? You can remove the relayhost setting and reload postfix. Postfix won't do this automatically, but you could use a monitoring script of some type. Before you do this ask yourself the question of why use a relayhost at all if you don't mind delivering the mail directly. -- Noel Jones
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