SMTP 25 open for user

thiagotgc

I understand that SMTP should be blocked for the end user on port 25, with SSL/TLS or without.

The only shipping ports must be 465 or 587.

Port 25 must be open only between MX servers, and not to the end user to send e-mails.

How to fix this gap?

aaPanel_Captain

can only ask the server operator to cancel the restriction on port 25, and the sending and receiving is based on the mta protocol

thiagotgc

aaPanel_Captain

I have no problems with locking port 25.

I just wish that the users could not authenticate for it.

I want them to use only 587 or 465.

aaPanel_Captain

thiagotgc If you need port 465, you need to deploy an SSL certificate in the post office service. If you need port 465, you need to deploy an SSL certificate in the post office service. It is recommended to apply for a pan-domain certificate

thiagotgc

aaPanel_Captain

I have already deployed SSL.

But I don't think you understand yet.

My problem is not to make SMTP work on port 587/465.

The problem is that the end user (anyone) can configure SMTP on port 25 and authenticate.

The correct thing is to have port 25 blocked for this, and leave only 587 and 465 for this job

aaPanel_Captain

thiagotgc hello， do you want to only allow mail users to connect to port 465 and 587 and refuse them to connect to port 25? If so, let's see how to deal with this problem

thiagotgc

aaPanel_Captain

Exactly!

But it is not why I would like to, this is what should be the right behavior!

TrK

You can create a firewall(like iptables or firewall-cmd) rule blocking everyone except your defined IP address.

thiagotgc

TrK

Port 25 cannot be blocked, because the servers use it to communicate and send messages.

Port 25 must be released, but prevented from accepting user logins.