+++ Dan Egli [exim-users] <16/08/01 14:10 -0600>:
> Unfortunately, some MTAs (i.e. MS Exchange) don't do that. Their behavior is
> to grant 250s to the commands, then after the . that terminates the "data"
> mode, it checks addresses and returns a 5xx at that point. DUMB I know, but
> true.
Not exactly dumb. Take the case of a mailhub setup where a single MTA / set
of MTAs accepts mail - only to pass it on blindly to other MTAs for further
delivery. So, even if you get a 250 initially, another MTA somewhere down
the line might return a 550.
-suresh
