how can I change port 25 for other (Postfix)

tomkis · 03-17-2008, 01:55 PM

Hi I have a problem with sending mail, I can send it to myself, but doesn't work for outside world. I am using dyndns, but I am not sure if my ISP is blocking port 25, Dovecot works fine I can receive my mails. I know that there was another thread, but I am just wondering if it is possible in postfif/main.cf

slozzy · 03-17-2008, 04:56 PM

I have the exact same problem. I posted in the newbie thread though. I would just like 1 of 3 virtual domains to relay the mail via other smtp. I am going to keep searching for the solution.

trickykid · 03-17-2008, 04:57 PM

Probably not blocking but most ISP's and mailservers will deny DHCP enabled hosts, which you probably have.

slozzy · 03-18-2008, 11:49 PM

I'm still able to telnet my.mailhost.com [port] to my mail server and test fine.

trickykid · 03-19-2008, 09:36 AM

Quote:

Originally Posted by slozzy

I'm still able to telnet my.mailhost.com [port] to my mail server and test fine.

It's not a matter of your port being blocked. Most ISP's and other mail servers do not allow email or messages from mail servers with DHCP and no reverse DNS of the actual domain to be delivered. This is a way to block potential spam(mers) that might have taken control of a host that isn't intended to be a mailserver but to be used to send email.

farslayer · 03-19-2008, 02:48 PM

If you are running your mail server on a port other than 25, how is my mail server supposed to know that ? My mail server would try to send mail to your mail server using port 25. there is no way to automatically tell my mail server to send to a different port when it attempts to connect to your mail server, that I am aware of.

And yes, my mail server denies mail from Dynamically assigned addresses and server with no reverse DNS as well. Still see thousands of SPAM messages hit the filters daily.

billymayday · 03-19-2008, 03:35 PM

The easiest way around this, unless for some reason it really doesn't suit, is to relay outgoing mail via your ISP's smtp server. All ISP's that offer mail accounts offer this capability, and it resolves all the issues outlined above regarding reverse DNS, port numbers, etc.

Check your ISP's details for getting your email - they will have given you details of their smtp server and pop server.

slozzy · 03-19-2008, 08:41 PM

Yes this is what I'm trying to do. Get the mail out on a port other than port 25 to my hoster's SMTP. The email will go out from there on port 25. Previously the PTR and MX records were setup and I was sending mail directly but now have to make this change for the client.

billymayday · 03-19-2008, 09:20 PM

No, your ISP's smtp will listen on port 25. Thsi is different from your domain name hoster which is where your other post is at.

Is there a reason why you don't use your ISP's smtp? The only downside is it may show the connection comming from a server that isn't yours to recipients, but who cares.