Hello all,

So far everything works well except for the mail server.

I send an email from Gmail and it got delivered I received it on my Outlook but when I try to reply to the same email it send without any issue but it is not delivering to my Gmail.

I'm not using and SPAM Filter software and all servers running smoothly "Postfix, Dovecot, Rspamd"

I have all clean records Dkim, SPF, MX, A

Even SSL properly configured

OS: Debian 10

Log File

Oct 25 11:15:41 server8790 dovecot: imap(booking@example.com)<25698><+GwZrC/Pi+MoYYoF>: Logged out in=159 out=1896 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Oct 25 11:15:58 server8790 postfix/smtpd[25761]: warning: error opening chain file: /etc/ssl/private/ssl-cert-snakeoil.key: No such file or directory
Oct 25 11:15:58 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:15:58 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:16:02 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:16:02 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:16:12 server8790 dovecot: imap-login: Login: user=<booking@example.com>, method=PLAIN, rip=40.97.138.5, lip=xxx.xxx.xxx.x, mpid=25772, TLS, session=<ajX3rS/PODsoYYoF>
Oct 25 11:16:13 server8790 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=40.97.138.5, lip=xxx.xxx.xxx.x, session=<GR0Ari/Pe14oYYoF>
Oct 25 11:16:13 server8790 dovecot: imap(booking@example.com)<25772><ajX3rS/PODsoYYoF>: Logged out in=159 out=1896 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Oct 25 11:16:43 server8790 dovecot: imap-login: Login: user=<booking@example.com>, method=PLAIN, rip=40.97.138.5, lip=xxx.xxx.xxx.x, mpid=25787, TLS, session=<AN3Try/P/mIoYYoF>
Oct 25 11:16:44 server8790 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=40.97.138.5, lip=xxx.xxx.xxx.x, session=</g3bry/PND8oYYoF>
Oct 25 11:16:44 server8790 dovecot: imap(booking@example.com)<25787><AN3Try/P/mIoYYoF>: Logged out in=159 out=1896 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Oct 25 11:17:08 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:17:08 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:17:11 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:17:11 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:17:15 server8790 dovecot: imap-login: Login: user=<booking@example.com>, method=PLAIN, rip=40.97.138.5, lip=xxx.xxx.xxx.x, mpid=25800, TLS, session=<CzyxsS/P1UcoYYoF>
Oct 25 11:17:15 server8790 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=40.97.138.5, lip=xxx.xxx.xxx.x, session=<lLi4sS/PxHUoYYoF>
Oct 25 11:17:15 server8790 dovecot: imap(booking@example.com)<25800><CzyxsS/P1UcoYYoF>: Logged out in=159 out=1896 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Oct 25 11:17:43 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:17:43 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:17:46 server8790 dovecot: imap-login: Login: user=<booking@example.com>, method=PLAIN, rip=40.97.138.5, lip=xxx.xxx.xxx.x, mpid=25814, TLS, session=<hiiMsy/PEoQoYYoF>
Oct 25 11:17:46 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:17:46 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:17:46 server8790 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=40.97.138.5, lip=xxx.xxx.xxx.x, session=<65eTsy/P/lcoYYoF>
Oct 25 11:17:46 server8790 dovecot: imap(booking@example.com)<25814><hiiMsy/PEoQoYYoF>: Logged out in=159 out=1896 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Oct 25 11:18:18 server8790 dovecot: imap-login: Login: user=<booking@example.com>, method=PLAIN, rip=40.97.138.5, lip=xxx.xxx.xxx.x, mpid=25817, TLS, session=<sYxxtS/P8xkoYYoF>
Oct 25 11:18:18 server8790 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=40.97.138.5, lip=xxx.xxx.xxx.x, session=<IKB5tS/PxZMoYYoF>
Oct 25 11:18:18 server8790 dovecot: imap(booking@example.com)<25817><sYxxtS/P8xkoYYoF>: Logged out in=159 out=1896 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Oct 25 11:18:49 server8790 dovecot: imap-login: Login: user=<booking@example.com>, method=PLAIN, rip=40.97.138.5, lip=xxx.xxx.xxx.x, mpid=25824, TLS, session=<DFFPty/PP80oYYoF>
Oct 25 11:18:49 server8790 dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=40.97.138.5, lip=xxx.xxx.xxx.x, session=<5KZXty/Pg3woYYoF>
Oct 25 11:18:50 server8790 dovecot: imap(booking@example.com)<25824><DFFPty/PP80oYYoF>: Logged out in=159 out=1896 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
Oct 25 11:18:53 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:18:53 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:18:56 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:18:56 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:19:28 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:19:28 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:19:32 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:19:32 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:20:38 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:20:38 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:20:45 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:20:46 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:21:12 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:21:12 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:21:19 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:21:19 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:22:22 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:22:22 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:22:29 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:22:29 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:22:57 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:22:57 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:23:00 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:23:00 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:24:07 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:24:07 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:24:14 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:24:14 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:24:41 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:24:41 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:24:44 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:24:44 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:25:51 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:25:51 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:25:54 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:25:54 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4
Oct 25 11:25:58 server8790 postfix/anvil[25764]: statistics: max connection rate 2/60s for (smtp:xxx.xxx.xxx.x) at Oct 25 11:17:43
Oct 25 11:25:58 server8790 postfix/anvil[25764]: statistics: max connection count 1 for (smtp:xxx.xxx.xxx.x) at Oct 25 11:15:58
Oct 25 11:25:58 server8790 postfix/anvil[25764]: statistics: max cache size 1 at Oct 25 11:15:58
Oct 25 11:26:26 server8790 postfix/smtpd[25761]: warning: hostname ip245.tervelnet.com does not resolve to address xxx.xxx.xxx.x: Name or service not known
Oct 25 11:26:26 server8790 postfix/smtpd[25761]: connect from unknown[xxx.xxx.xxx.x]
Oct 25 11:26:29 server8790 postfix/smtpd[25761]: warning: unknown[xxx.xxx.xxx.x]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Oct 25 11:26:29 server8790 postfix/smtpd[25761]: disconnect from unknown[xxx.xxx.xxx.x] ehlo=1 auth=0/1 rset=1 quit=1 commands=3/4

NOTE: Domain name and IP address filtered "example.com / xxx.xxx.xxx.x" for security

Oh okay now I got a delivery error report from outlook

From: "booking@example.com" booking@example.com
To: "gmailname@gmail.com" gmailname@gmail.com
Subject: Re: Test email
Thread-Topic: Test email
Thread-Index: ATg1RUY0lQPIiuRvdMVOOSnwMPN1mb8o6kHB
Date: Mon, 25 Oct 2021 16:07:43 +0000
Message-ID:
CY4PR16MB1782D79F7182462097B68013A9839@CY4PR16MB1782.namprd16.prod.outlook.com
References: F5BEC8E4-CD9A-FA48-A5EE-A5585C8030C8@hxcore.ol
In-Reply-To: F5BEC8E4-CD9A-FA48-A5EE-A5585C8030C8@hxcore.ol
Content-Language: en-US
X-MS-Has-Attach:
X-MS-Exchange-Organization-SCL: -1
X-MS-TNEF-Correlator:
X-MS-Exchange-Organization-RecordReviewCfmType: 0
Content-Type: multipart/alternative;
boundary="000_CY4PR16MB1782D79F7182462097B68013A9839CY4PR16MB1782namp"
MIME-Version: 1.0

--000_CY4PR16MB1782D79F7182462097B68013A9839CY4PR16MB1782namp
Content-Type: text/plain; charset="us-ascii"

Hey,

Thank you

Regards

From: gmailname@gmail.com gmailname@gmail.com
Date: Monday, October 25, 2021 at 8:02 PM
To: example booking@example.com
Subject: Test email
Hello,

This is a test email

Thank you

--000_CY4PR16MB1782D79F7182462097B68013A9839CY4PR16MB1782namp
Content-Type: text/html; charset="us-ascii"

<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style></style>
</head>
<body lang="EN-US" link="#0563C1" vlink="#954F72" style="word-wrap:break-word">
<div class="WordSection1">
Hey,<o:p></o:p>
<o:p> </o:p>
Thank you <o:p></o:p>
<o:p> </o:p>
Regards<o:p></o:p>
<o:p> </o:p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
From:
gmailname@gmail.com <gmailname@gmail.com> 
Date: Monday, October 25, 2021 at 8:02 PM 
To: example <booking@example.com> 
Subject: Test email<o:p></o:p>
</div>
Hello,<o:p></o:p>
<o:p> </o:p>
This is a test email<o:p></o:p>
<o:p> </o:p>
Thank you<o:p></o:p>
</div>
</body>
</html>

--000_CY4PR16MB1782D79F7182462097B68013A9839CY4PR16MB1782namp--

more technical details displayed on this report email

Technical details
SmtpSubmissionTransientInvalidErrorCodeException: Smtp submission failed. Server 'mail.example.com' Port '143'. --> Unexpected SMTP server response. Expected: -1, actual: -1, whole response: HELO BAD Error in IMAP command received by server.

Failure code: 54bc