* on the Wed, Jan 31, 2007 at 09:45:59AM +0000, Peter Bowyer wrote: >> No one has mentioned why sender callouts without a null sender are "bad" >> yet. As far as I can see the worse that can happen is, a remote mail >> server connects to yours, and sends a "MAIL FROM" and a "RCPT TO". You >> then connect to the MX for the domain in the MAIL FROM, and do the same, >> using the value of the "RCPT TO" in the mail from of the callout. They >> then connect back to you to do a sender callout themselves. Then it >> stops due to the cache... And this would only happen in the rare >> circumstances that both servers are using sender callouts... > If your server is performing a sender callout, it's because the sender > isn't in its cache. When the reverse callout comes back, the sender is > the same and still isn't in the cache because the first callout hasn't > completed, so the loop continues.
Crap. Of course. This only happens in the circumstances where both servers are using callouts without null senders though. I guess that's why I've not seen it yet. I need to rethink this now. Mike -- ## 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/
