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Change port 25 to 2525

Posted on 2011-10-03
Medium Priority
Last Modified: 2013-08-20
I have a small program which monitors the UPS. If the power fails, it can send an email. It is doing so through port 25.
My ISP is blocking it, and offers port 2525 as an alternative.

In my Draytek router I can map port 2525 to 25, but that is INBOUND. I need Outboud.

Is there a way, to change the outbound port to 2525, or another solution? (a commercial VPN like Strong VPN, and send the mail there, is an option, but not preferred yet).

WinXP as  a OS.

(wild idea: Run Linux mail server in a virtual box, and have it relayed to port 25)?
Question by:veermanh
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LVL 33

Accepted Solution

Dave Howe earned 2000 total points
ID: 36906139
that would be a solution, but its overkill - you can run a mailserver on windows too of course, but all you really need is some sort of portmapper.

I am assuming given you mention your need to run linux in virtua, that you are on windows, so might I suggest this one:


just map 25 to <upstreamhost>:2525 and point your alert software to localhost - it will automatically forward that to 2525 on the server you specified.

Author Comment

ID: 36906683
Perfect. I will try it, and see if it works.

In the description it seems to do what I want.

Now I need to be sure, it can do outbound as well....
LVL 33

Expert Comment

by:Dave Howe
ID: 36908547
that would be outbound only, really. you are connecting to port 25 on "localhost" and the software forwards to port 2525 on your target mailhost (unusual though. normally an isp will supply a smarthost on 25; lots of mail clients can't specify a non-port-25 host.

which ISP is it?

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Author Comment

ID: 36908640
It is an ISP in Ukraine. For them it seems "easier" to block port 25 in stead of using other means (read: costing money)...

And yes, this specific application cannot specify other port than 25.
LVL 33

Expert Comment

by:Dave Howe
ID: 36909361
Well, yes, a lot do that (in the uk for example, the dominant telephony provider Brutish Telecomm block port 25 outbound. But they allow 25 to their own mail server (mail.btconnect.com) so that their own customers can send email.

I would pick one at random and look, but given you have more than 250 ISPs in the Ukraine, the odds of me getting the right one are low :)
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Expert Comment

ID: 39418043
I've requested that this question be deleted for the following reason:

Not enough information to confirm an answer.
LVL 33

Expert Comment

by:Dave Howe
ID: 39418044
not seeing why this is unconfirmed? I gave an answer, and several follow-up comments. a quick check would show the utility recommended can port forward to other ports as requested by OP?

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