topic Email ports in Tech Help - Software/Hardware etc

Email ports

7up — Wed, 05 Dec 2018 15:22:02 GMT

One for the advanced folks... maybe even plusnet's tech staff...

I've been mulling over my email server and for various reasons, it would be handy to run it on a different port than the normal port 25 that smtp uses.

Is it possible to use a port number on an email address like you can for a domain when making a http request? - eg user@domain.com:27 ? Or can that be set via an MX record?

To me that seems quite straight forward and logical.. but not sure if it works and i can't find anything online about it.

Re: Email ports

ReedRichards — Thu, 06 Dec 2018 07:58:33 GMT

Well the Plusnet SMTP server can use either port 25 or port 587. But in order to relay email via the Plusnet SMTP server you have to specify which of these two ports to use. Are you saying that you would like to override the use of port 25 on your own SMTP server because you don't know how to change the server settings?

Re: Email ports

dvorak — Thu, 06 Dec 2018 08:40:40 GMT

The answer is pretty much no, RFC821 defines the port for transmitting of email as 25.
There are other services that will listen for your mail on 25 and forward to another port if you so desire, but then you might was get a small VPS for ~ £5 a month and run a mail server on it.

Re: Email ports

7up — Thu, 06 Dec 2018 18:59:35 GMT

@ReedRichards wrote:

Well the Plusnet SMTP server can use either port 25 or port 587. But in order to relay email via the Plusnet SMTP server you have to specify which of these two ports to use. Are you saying that you would like to override the use of port 25 on your own SMTP server because you don't know how to change the server settings?

I know how to specify which port to use in my client program such as outlook etc - that's not a problem.

Yes I'd like to override the default port 25 on my own email server - again that isn't an issue setting it, but what i want to know is whether or not other mail systems would recognise the port being included on the end of an email address. I suppose the only real way to find out is expose my mail server to the web and send emails to it and see what happens.. I was just hoping for a quicker and easier answer.

Re: Email ports

dvorak — Thu, 06 Dec 2018 21:03:11 GMT

You can try 2525, that should work and also will support tls. (Not supported by IETF nor IANA though)