On 11/14/11 7:35 AM, "Marc Perkel" <[email protected]> wrote:
>The way I determine if the primary is down is to do a forward callout. >If it returns a message that it can't connect or complete verification >then the server is offline and the backup should take the message. if it >is verified as good then the primary is online and should return a defer >- 4xx error. Some broken MTAs-- I'm thinking Qmail, but I may be mistaken-- will "lock on" to an MX that responds with a 4xx error and will only retry sending to that server instead of going through the normal progression of MX records again. In that case, a temporary outage on the primary could lead to a message never being delivered. Also, be aware that sometimes routing issues, firewall problems, etc. may cause the primary to be unreachable from one site but reachable from the secondary; again, this could cause delivery problems. Just a couple of things to consider. -- Dave Pooser Cat-Herder-in-Chief, Pooserville.com "If you think bringing a wet noodle to an Amish rake fight makes you 'better armed' for it, then you have a funny understanding of how the universe works." -- Al Iverson -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
