Hello all, we have a single Exchange 2003 server and we cannot send to larger ISPs. We continuously get send message errors for AOL, Comcast, SBC Yahoo, SBCGlobal, and AT&T. I googled this and have seen posts about these ISP blocking port 25 (except when from their internal servers) to help ccontrol spam. Is this true? What I have seen on the net is the different ISPs are using different ports to receive inbound e-mails. If this is not the case, what else could be the problem? I am not on any blacklists. I have an IP address exclusively for our exchange server. I am not an open relay. Ani suggestions?
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Large ISPs blocking port 25?