BTInternet sending mail peroblem?

[Pens]

I have two users with different domains on my server who for the past 10 days have been unable to send emails.

Both are in the UK and use BTInternet as their ISP, they have no problem receiving emails.

The Brute force monitor reports:
025-06-22T14:28:24.746070+02:00 server dovecot[2786430]: pop3-login: Disconnected: Connection closed (auth failed, 1 attempts in 0 secs): user=<sro@{Domain}.com>, rip={x.x.x.x}, lip={Server IP}, session=<WZZIOyg4EMdWrBJx>

The EXIM Log reads
2025-06-23 14:51:27 unexpected disconnection while reading SMTP command from (smtp.{Domain}.com) [{x.x.x.x}] D=7s2025-06-23 14:51:27 H=(mail.{domain}.com) [{x.x.x.x}] incomplete transaction (connection lost) from &lt;omtyfstz@{domain}.com&gt;2025-06-23 14:51:27 unexpected disconnection while reading SMTP command from (mail.{domain}.com) [{x.x.x.x}] D=7s

Is it possible that BTInternet are blocking port 465 SMTP calls?
I have set up mail accounts on their domains and have no problems receiving emails using Orange France as my ISP.
They can send emails from WebMail, using the same log in information.

I remember years ago Orange France blocked port 25 and my host had to set up port 2525 for me, I have seen some very old DA forum posts about port 2525 but not a way to set it up on.

Anyone any ideas before I pull what's left of my hair out?

 

[Richard G]

Is it possible that BTInternet are blocking port 465 SMTP calls?

I hightly doubt that as this is still the international known and used SSL port. Also the connection is already made, because it says "unexpected disconnection while reading smtp command". It has to be connected to be able to disconnect as far as I know. There is also no reason for a port 465 block as there was for port 25.

Anyway, you can easily test if some block is set up (again which I highly doubt) by changing the port to port 587 which is also a well known modern SMTP port. If it works on 587 and not on 465, then it's either a block or some ssl/tls issue.

So I would say test with port 587 and see what happens.

 

[Pens]

I hightly doubt that as this is still the international known and used SSL port. Also the connection is already made, because it says "unexpected disconnection while reading smtp command". It has to be connected to be able to disconnect as far as I know. There is also no reason for a port 465 block as there was for port 25.

I agree but I'm clutching at straws

Anyway, you can easily test if some block is set up (again which I highly doubt) by changing the port to port 587 which is also a well known modern SMTP port. If it works on 587 and not on 465, then it's either a block or some ssl/tls issue.

So I would say test with port 587 and see what happens.

Rather than changer in server port (I couldn't see how to do it anyway on a domain by domain basis) I changed the SMTP port on my mail client and got exactly the same error message.

I'll get the users to make sure they are using port 465.

Thanks again for all your help

Nick

 

[Richard G]

I changed the SMTP port on my mail client

Yes sorry, ofcourse I meant in the mail client because the server always uses both ports 465 and 587 by default, unless you changed that.
Pity you got the same error message.
I understand you're clutching at straws, as would I do probably in such case.

I'll get the users to make sure they are using port 465.

It normally would make no difference and should work both as well.

However this is mentioned at first:

Connection closed (auth failed, 1 attempts in 0 secs):

That is a more clear cause of the issue.

You didn't upgrade Exim and Dovecot (and configs) maybe a day or 10 ago?
Are you sure it's not cause by the new required settings for SSL in authentication and encrypted passwords (unless customized)?

Maybe check this to be sure.

Version 1.676 | Directadmin Docs

DirectAdmin Knowledge Base

docs.directadmin.com

this is not only for port 25, the smtp authentication goes for all ports.

 

[Pens]

Yes sorry, ofcourse I meant in the mail client because the server always uses both ports 465 and 587 by default, unless you changed that.
Pity you got the same error message.

I got the error message using port 587 in the mail client.

It normally would make no difference and should work both as well.

465 works, 587 fails on all the hosted domains unless I change the connection security to STARTTLS from SSL/TLS

You didn't upgrade Exim and Dovecot (and configs) maybe a day or 10 ago?
Are you sure it's not cause by the new required settings for SSL in authentication and encrypted passwords (unless customized)?

Yes, I updated Exim but the Dovecot upgrade failed.
But why would the problems only occur with these two users on their own domains, when I can send through them?

Maybe check this to be sure.

Version 1.676 | Directadmin Docs

DirectAdmin Knowledge Base

docs.directadmin.com

this is not only for port 25, the smtp authentication goes for all ports.

Is the clue in /etc/exim.variables.conf ?

daemon_smtp_ports=25 : 587 : 465
tls_on_connect_ports=465

Nick

 

[Richard G]

587 fails on all the hosted domains unless I change the connection security to STARTTLS from SSL/TLS

587 is a STARTTLS port, I don't know which e-mail client you're using. In Outlook 2013 I set it to TLS and it works.
In Thunderbird it's set to STARTTLS.

I got the error message using port 587 in the mail client.

Oh then I probably thought wrongly because initially you thought port 465 was blocked because of errors in the exim logs. So I thought port 465 was having an issue.

But why would the problems only occur with these two users on their own domains, when I can send through them?

I'm just trying. It could be just by accident that it's just these two users still are using plaintext password, I didn't know if you checked with them.

Is the clue in /etc/exim.variables.conf ?

That's the default setting so that should be fine. Works on all my servers and I don't think you need to change server settings for just 2 customers from a specific ISP. But it is odd indeed.