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blocked port 25

I think my isp(comcast) blocks port 25, this makes setting up my mail server kinda difficult. No-ip offer a service called port reflecting or sumthing to that effect. I don't really wanna pay for that though, it's not expensive , im just poor. Does anyone know of any kind of workaround for this ? I really wanted to have my computer acting as my mail server.



even if you can get around it.. its almost pointless if you email friends and family on aol or hotmail.. why because they won't get it anyway. A lot of major ISPs are blocking all emailing coming from known residental IP blocks. I'm sure this includes you. The reason is that close to 90% of the spam comes from them

You could always make sendmail use another port its not hard


iptables -t nat -A PREROUTING -i eth0 -p tcp *newport* -j REDIRECT --to-port 25



that way, outside your network, you'd have to setup your mail client to use *newport* for smtp. its how i use it..


and yes, hijinx is right, you wont be able to send to most of the webmail based mail services.. eg, yahoo, excite etc etc.


thanks for the info guys



my ISP also blocks port 25 which i must say didn't make me happy... so i called them (tech support) and asked what can i do about it,


after 20 minutes of convincing them that i only needed port 25 for my forums (here) they informed me of their 'anonymous' smtp relay server,


perfect, all i need to do is forward mail through that server and it works just fine !


i would suggest that you contact your ISP and ask them do they provide a smtp relay server for their customers





thanks for the info i'll give em a call :)
well after finally gettting off my lazy ass and calling my isp, i was told that they don't block port 25. Funny thing though, when i run nmap on i can see that yes my mail port is indeed open, then i checked by nmapping, which sends it through no-ip an back to me. This time it shows up no port. Next i tried my actual ip, and once again my mail server doesn't show up. So basicly either im doing something wrong or my isp is straight up lying to me. am i reading my test results wrong? I mean if the port shows up locally as open but doesn't even showup from a remote standpoint then the only possible cause would be a prot block ? right ?

Often ISP's have relay SMTP servers if they block port 25 for their users.


To use them, set your MX records on your domain like this: 38400 IN MX 20 38400 IN MX 30


That way sending mail to will fail on the shortest metric and will then try the relay server. Your ISP's relay server will accept the mail and delivers it to your SMTP server.


I've had this working on ISP in the Netherlands...

I've just configured sendmail to act as a local smtp server only, (only listens on loopback interface) and I have registered, I tried sending mail from my smtp server to hotmail, it recieved it as junk mail, but yahoo recieves it fine, email is send like this: *



would you mind doing a howto (new post) on what you did step by step, noob friendly


i'd like to see it






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