SMTP server - two ports?

[ehavemann]

Some offsite / mobile users cannot send outbound mail on port 25 through my AMS box because their ISP restricts port 25 traffic to their own SMTP server. Is there any way to configure AMS to use the default SMTP port 25 AND an alternate port (like 26), so I can work around those ISP restrictions for those users?

[Code Crafters]

Yes, this can be achieved by simply setting your router to forward port 25 to your mail server port 25 and another port (e.g. 2525) to your mail server port 25 assuming you can set your router to different internal and external ports which most can. We are also planning on allowing multiple ports to be specified in the service settings in a future update.

[MikeG]

We had the same situation, but as the server is hosted by a 3rd party we couldn't change the router configurations easily.
Instead we use a small utility called PortTunnel (http://www.steelbytes.com) which maps incoming traffic on one port across to another port.
It costs $99 (£50) but does the job nicely.

[ehavemann]

I am aware of the router mapping option, but I'm not using a router - the AMS NIC on my dual-homed server has a public IP (The other NIC is behind a router that does support port forwarding etc., but we're using a separate ISP for the rest of the network and I can't have two default gateways in the server). And most of the lower-end routers (Linksys wireless, etc.) don't support that anyway. Will PortTunnel re-map port 2525 to port 25 on the same IP?

[Code Crafters]

There are many such port forwarding services available from most domain registrar hosts such as http://www.no-ip.com. I'm sure they do a port forwarding service to receive mail on whatever ports you want and forward them to your mail server on port 25. Many other users have used such services to get round their ISP not allowing them to listen on port 25 at all.

[MikeG]

Yes, we use PortTunnel to allow users to send mail via port 25 or via port 587. As far as AMS is concerned, it sees all the traffic arriving just on port 25.
When setting up a new mapping in PortTunnel, set the "In Port" to whatever port you want to use (ie 2525) and the "Out Port" to 25. Then set the "Out Target" to being 127.0.0.1

[ehavemann]

Thanks! MikeG re: the PortTunnel suggestion - it works as you said. The only problem is that it resides in my server's taskbar so I have to instruct server admins not to close it. Since my original post I moved my AMS server behind the firewall, but still had the same problem. My laptop users bring their machines in and out of the office. The firewall directs ports 25 and port 26 to AMS. Behind the firewall AMS only listens on port 25. This program (along with an Active Directory forward-zone that redirects mail.mydomain.com to local ip 192.168.1.5) lets my laptop users come and go without mucking around with mail settings or multiple profiles. I look forward to an AMS upgrade to handle this though.

[ehavemann]

I found a free alternative to PortTunnel that does the same job. It's at http://www.kmint21.com/free/

It's a tiny 5 Kb command-line program. The following command using this utility does the trick:
pm 026 127.0.0.1 25

It simply remaps port 26 traffic to port 25.