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How can you redirect your smtp traffic to another port than 25? My ISP blocks incoming traffic to port 25.

I've been using ZoneEdit.com for this purpose for years (incoming mail traffic goes to another port and I redirect it via my firewall internally to port 25), but with the new system I cannot do it anymore.

I'm not sure if I can do this by configuring MX and A records in the right way or if I need a SMTP redirecting service (such as rollernet.us)?

I'm not an expert in Zone records but generally I know my way around for website traffic.

Roalt
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3 Answers3

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There is no way to tell a sending server what port you're listening on using MX (or other records). You will have to use a reflector service. No-ip have a reflector service that will forward mail to a non standard port.

user9517
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  • I used to have all incoming mail to mydomain.com redirected to mygmailaccount@gmail.com. I set gmail to forward all my mail to myself@mymailserver.mydomain.com (so I have a backup!). Will this work too? It looks like I can only set an MX record on my whole domain, not on mymailserver.mydomain.com ? – Roalt Dec 29 '10 at 15:42
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    Forwarding emails to your own server won't work as none of the servers in the world know other port of your server. Setting MX record for a domain is all you can do in DNS but still all servers will use 25th port. You need to use reflector service of some kind and point your MX record to that reflector service. Then reflector service will basically forward everything that comes to it to your server. – MadBoy Dec 30 '10 at 14:48
  • If I understand correctly the mail reflector service costs $39.95/year at no-ip.com – Roalt Dec 30 '10 at 15:21
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Above 2 answer all had some drawbacks, so this is what I did:

  1. I created a free account at rollernet.us
  2. I created a separate domain (yes DOMAIN NAME!) to receive my email (say mailaccount.com)
  3. I setup rollernet.us to create a SMTP Redirection to port xxxx of my own server for this mailaccount.com
  4. I configured the MX mail servers for the domain mailaccount.com (in my case at zonedit.com) to let them be handled by Rollernet's. (mail.rollernet.us and mail2.rollernet.us)
  5. For all accounts where I receive e-mail, I set-up an E-mail forwarding to my gmail account (say mypersonal.account@gmail.com).
  6. I set-up a forwarding e-mail from gmail to myaccount@mailaccount.com
  7. I made sure my postfix on my personal servers handling incoming traffic.

It's a bit complex (before I only needed zonedit to forward it my my higher than 25 port number), but it works. Other drawback is that I sacrify one domain name to handle my emails.

Roalt
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  • Anyone with an easier solution will be a very good candidate to win the accepted answer award. – Roalt Jan 02 '11 at 19:39
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What email server are you using?

If your ISP is blocking it on 25, you can specify another PORT to be used in your MAIL Server config. In Exchange 2007 you would change it in the Receive and Send Connectors via EMC or powershell. http://www.exchangelog.info/2007/08/how-to-change-smtp-port-25-in-exchange.html

I think in Linux based email servers you may have to edit the config file and change the port.

You would then open that port on your firewall and redirect it to your internal IP Address of your Mail Server.

Hope that Helps

Mutahir
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  • Problem is his mail server will never get any emails since all other servers around the world won't knew that the port server has changed to some higher port. Email servers use 25 port and that's it. That's why @lain answer with reflector service is thing to go. – MadBoy Dec 29 '10 at 09:53
  • Dont understand the Down Vote, as this is possible without a reflector service too..... @MadBoy, you are right, I was answering along the lines on how to change the port in your MAIL Server config (as Port 25 is blocked). On most routers you can specifiy that any traffic coming for Port 25 for 192.168.1.x should be redirected to Port 2525 192.168.1.x - this can be done without a reflector service too - No Offence to Iain as he has always provided me with helpful answers. – Mutahir Dec 29 '10 at 10:10
  • The problem is not my own mail server, but telling the world that my mailserver is on a different port. I can configure my mail server to use any port, but what I did was say to my firewall to redirect port 1234 (or any other) to internal port 25. – Roalt Dec 29 '10 at 15:37
  • another option can be is to use your ISP as SMTP Smart host, so you send and receive via them. if they allow you to (Most ISPs would). – Mutahir Dec 29 '10 at 16:17
  • you can't tell the world that your mail server uses different port using your own firewall since HIS ISP doesn't allow that traffic to ever hit the 25 port. That port is never reachable from anywhere so his router doesn't see any traffic on that port. So without using some kind of reflector service or smtp smart host at some provider service he can't do anything. – MadBoy Dec 30 '10 at 14:45