On exchange 2003 I want to listen for smtp on port 25 only so that * anonymous login is only allowed from certain internal IPs * authenticated login is allowed from everywhere

I can't see how to do this. Any IP filtering seems to affect both anonymous and authenticated login in the same way. Any ideas?

1 Answer 1


unfortunately that isn't possible. But you could create a second virtual SMTP server, just not using the same port and local IP. You'd need to either use a different SMTP port instead of 25 or bind the two virtual SMTP servers to different local network cards / IPs.

  • Thanks! Good to know that. I'm using port 587 now for authenticated users with the down side of more configuration effort on clients but it has the advantage that I can IP-filter port 25 on the real firewall instead of fooling around on this exchange box.
    – rudimeier
    May 12, 2015 at 21:50

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