SOLVED Sending to Gmail error did not encrypt this message

[Akylas]

Hello,

We experiencing unencrypted messages problem for all outgoing email messages from CPanel users to GMail. GMail shows received email messages from our server with red lock and notification:
security: XXX did not encrypt this message.

We have checked all configurations and tried to send emails from Webmail (Horde, Roundcube) and via SMTP with enabled SSL/TLS, but still no luck.

Telnet from our CPanel server to google mail server:

Trying 64.233.161.27...
Connected to gmail-smtp-in.l.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP s206-v6si4343957lja.329 - gsmtp
ehlo testing
250-mx.google.com at your service, [xxx.xxx.xxx.xxx]
250-SIZE 157286400
250-8BITMIME
250-ENHANCEDSTATUSCODES
250 SMTPUTF8

Email sending log (with server hostname changed to xxx.server.net, sender domain to domains.com, sender email to [email protected] and receiver email to [email protected]):

2018-05-08 22:43:11 [10931] SMTP connection from [::1]:53448 I=[::1]:587 (TCP/IP connection count = 2)
2018-05-08 22:43:12 [11049] H=(xxx.server.net) [::1]:53448 I=[::1]:587 Warning: Sender rate 1.0 / 1h
2018-05-08 22:43:13 [11049] 1fG8W0-0002sD-EC H=(xxx.server.net) [::1]:53448 I=[::1]:587 Warning: Message has been scanned: no virus or other harmful content was found
2018-05-08 22:43:13 [11049] 1fG8W0-0002sD-EC <= [email protected] H=(xxx.server.net) [::1]:53448 I=[::1]:587 P=esmtpsa X=TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128 CV=no SNI="localhost" A=dovecot_plain:[email protected] S=763 M8S=0 [email protected] T="One more tima testing" from <[email protected]> for [email protected]
2018-05-08 22:43:13 [11055] cwd=/var/spool/exim 3 args: /usr/sbin/exim -Mc 1fG8W0-0002sD-EC
2018-05-08 22:43:13 [11055] 1fG8W0-0002sD-EC Sender identification U=domainc D=domain.com [email protected]
2018-05-08 22:43:13 [11055] 1fG8W0-0002sD-EC SMTP connection outbound 1525808593 1fG8W0-0002sD-EC domain.com [email protected]
2018-05-08 22:43:14 [11049] SMTP connection from (xxx.server.net) [::1]:53448 I=[::1]:587 closed by QUIT
2018-05-08 22:43:14 [11055] 1fG8W0-0002sD-EC => [email protected] F=<[email protected]> P=<[email protected]> R=dkim_lookuphost T=dkim_remote_smtp S=2081 H=gmail-smtp-in.l.google.com [64.233.161.26]:25 I=[xxx.xxx.xxx.xxx]:37210 C="250 2.0.0 OK 1525808595 t66-v6si12294885lje.83 - gsmtp" QT=2s DT=1s
2018-05-08 22:43:14 [11055] 1fG8W0-0002sD-EC Completed QT=2s

Please help us with this issue.

Thank you!

 

[cPanelMichael]

Telnet from our CPanel server to google mail server:

Trying 64.233.161.27...
Connected to gmail-smtp-in.l.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP s206-v6si4343957lja.329 - gsmtp
ehlo testing
250-mx.google.com at your service, [xxx.xxx.xxx.xxx]
250-SIZE 157286400
250-8BITMIME
250-ENHANCEDSTATUSCODES
250 SMTPUTF8

Hello @Akylas,

It looks like the STARTSSL command is missing. Here's how the same command looks from a test system:

# telnet gmail-smtp-in.l.google.com 25
Trying 64.233.180.27...
Connected to gmail-smtp-in.l.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP a10-v6si1874069oic.405 - gsmtp
ehlo testing
250-mx.google.com at your service, [208.74.121.106]
250-SIZE 157286400
250-8BITMIME
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8

I've seen this issue arise in the past when a hosting provider/data center utilized Cisco hardware with SMTP/packet inspection enabled. Can you check with your hosting provider or data center to see if they have implemented any form of SMTP/packet inspection?

Thank you.

 

[Akylas]

Thank you for your fast reply.

Yes this was the case of this problem. And they refused to disable this option. It's time to move to other datacenter...

Thank you!

 

[cPanelMichael]

Hello @Akylas,

While it's unfortunate your data center was unwilling to help, I'm glad to see you were able to confirm the cause of the issue.

Thank you for updating us with the outcome.

 

[Raviraj saini]

I am getting the similar problem but not able to fix that.. please let me know how I can fix that.. I have 4 other servers but didn't have this issue on another server.

 

[cPanelMichael]

I am getting the similar problem but not able to fix that.. please let me know how I can fix that.. I have 4 other servers but didn't have this issue on another server.

Hello @Raviraj saini,

Can you let us know the results when running the below command from your cPanel & WHM server's command line?

telnet gmail-smtp-in.l.google.com 25

Thank you.