SOLVED Dovecot Login or pop3 method PLAIN

[email protected]

Well-Known Member
Aug 3, 2016
59
5
8
Everywhere
cPanel Access Level
Root Administrator
Hello,

I have a question about how a user can login to exim/dovecot without pop3/imap/webmail login!

I see from logs: /var/log/maillog that users connects as:

Code:
pop3-login: Login: user=<[email protected]>, method=PLAIN, rip=xxx.xxx.xxx.xxx, lip=xxx.xxx.xxx.xxx, mpid=SOMENUMBER, TLS, session=<SomeID>
But also from /var/log/exim_mainlog I noticed that a user that is not before connected (send mail) as pop3/imap/webmail login they can send message as:
Code:
SMTP connection from [xxx.xxx.xxx.xxx]:1020 (TCP/IP connection count = 1)
P=esmtpsa X=TLSv1:DES-CBC3-SHA:168 CV=no A=dovecot_login
SMTP connection from ISP notes (PC USER ID) [xxx.xxx.xxx.xxx]:1020 closed by QUIT
Is possible a user send mail from smtp without connect before as pop3/imap?

What is the difference that I see in logs from A=dovecot_login vs A=dovecot_plain

Some users do that and some other no.

Can please explain how can they use SMTP connection to send email without login to pop3/imap/webmail?

A mail client as outlook/thunderbird do that?

I want to be sure that this connection is legitimate and not something else... From the logs seems is legitimate but how they can do that?

Thank you very much!
 

cPanelMichael

Administrator
Staff member
Apr 11, 2011
47,909
2,228
463
Hello,

Logging in via POP3/IMAP is not required before sending an email via SMTP. The user simply needs to authenticate via SMTP with valid credentials to send a message.

Regarding the delivery of messages, note the following from our Mail FAQ document:

What software does cPanel & WHM use for its mail servers (SMTP, POP, IMAP)?
cPanel & WHM version 58 and later uses Dovecot as the local mail delivery agent. Exim the mail transfer agent (MTA) receives inbound messages, connects to Dovecot via LMTP (Local Mail Transport Protocol), and Dovecot delivers the message. If LMTP is unavailable, the system uses the dovecot_lda mail delivery agent to deliver messages.

Earlier versions of cPanel & WHM used Exim as both the mail transfer agent and the local delivery agent.
Thank you.
 

[email protected]

Well-Known Member
Aug 3, 2016
59
5
8
Everywhere
cPanel Access Level
Root Administrator
Hello @cPanelMichael !

Your answer help me clear and understand how exim/dovecot works after 58 version!

The user simply needs to authenticate via SMTP with valid credentials to send a message.
Can please give me an example how I can make an SMTP authentication without POP3/IMAP login? I use thunderbird as mail client and before send messages every time I have imap or pop3 authentication...

I want just to test from my part that behavior!

Thank you!
 

cPanelMichael

Administrator
Staff member
Apr 11, 2011
47,909
2,228
463
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