Configuring an alternative port for SMTP access

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Configuring an alternative port for SMTP access


It's increasingly common for ISP's (such as BE Internet, Orange Internet, O2) and telephony providers to block SMTP access to mailservers other than their own or to actively proxy SMTP traffic when you are connected to the Internet through their network.

This can lead to problems as often remote workers will want to ensure email they send is tracked through MDaemon or they are unable to authenticate with MDaemon successfully before sending email as the ISP has proxied this traffic and the authentication credentials are never passed to MDaemon.

As these companies tend to only monitor the default SMTP port (TCP 25) for such access you can often workaround this limitation by opening another port to the Internet that MDaemon will also listen for incoming SMTP connections on and configure your users email clients to send email on this port instead.


There are two ports in MDaemon that will enable this - TCP 366 (ODMR) and TCP 587 (MSA) - and both these ports are already active in MDaemon at Setup -> Default Domain / Servers -> Ports. It's therefore just a case of making this port accessible to the Internet to allow remote client machines to access it. This is typically achieved using a "port forward" in your router/firewall and is a useful site which covers how to configure port forwarding on almost every router type hardware device.

Once you've opened the port to the Internet it is now necessary to configure those remote email clients to send email on this port:


1. Click on Tools -> Email Accounts and choose "Next" when the Email Accounts Wizard appears.
2. Highlight the account you wish to change and then click on the "Change" button.
3. Click on "More Settings" and then click on the "Advanced" tab.
4. Now change the Outgoing Server (SMTP) port value from 25 to either 366 or 587 (depending on the port you've opened)
5. Click "OK" on each window until you are back at the Wizard window and then click "Finish".

Outlook Express:

1. Click on Tools -> Accounts -> Mail and select the email account you wish to modify, then click Properties.
2. Click on the "Advanced" tab.
3. Now change the Outgoing Server (SMTP) port value from 25 to either 366 or 587 (depending on the port you've opened)
4. Click "OK" to save the change.

Security Considerations:

1. These external email clients will also need to be configured to authenticate with MDaemon before sending email and this article details how to achieve this -

2. Any email server which has SMTP accessible from the Internet is susceptible to being used by unknown users to 'spoof' email out through the server claiming to be a user at the local domain name.
It's therefore important to ensure that if you open either port 25 (SMTP), port 366 (ODMR) or port 587 (MSA) to the Internet that you apply IP Shielding in MDaemon as detailed in this article -