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Old 18th July 2009
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jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 7,977
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Correct.

Port 25 is used for SMTP services. It is expected that the IP is a static address, and referenced by an associated MX record from an Internet-facing DNS server.

Your ISP is blocking port 25, most likely because you are in a dynamic IP address pool, and such pools are filled by millions of "zombie" platforms pumping spam to the world. Broadband users with Windows, mainly. ISPs will block not only outbound to port 25 (which would actually be helpful in curbing spam), they often block inbound port 25 (since dynamic users wouldn't normally use it).

You can either buy a static IP address from your ISP that includes an unblocked port 25, somehow convince your ISP to unblock port 25 (highly unlikely), buy an alternative relaying service, switch to another service provider, or give up on running a public access MTA.
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