Okay, let me check on that and update you.

The following parts of the log clearly suggests that the email has been successfully delivered to the gmail SMTP (smtp.google.com)

Sep 3 09:18:17 mail postfix/smtp: 64E1BF25B20: to=<sreeandsree19@gmail.com>, relay=gmail-smtp-in.l.google.com:25, delay=2.2, delays=0.03/0/1.5/0.61, dsn=2.0.0, status=sent (250 Queued id=0x2000dc7f)
Sep 3 09:18:17 mail postfix/qmgr: 64E1BF25B20: removed

Sep 3 09:18:21 mail postfix/smtp: 1C42DF28106: to=<sreehari@phykon.com>, relay=smtp.google.com:25, delay=2.1, delays=0/0/1.6/0.51, dsn=2.0.0, status=sent (250 Queued id=0x2000dc81)

Therefore, it is nothing related to CE. You have to look into other issues (DNS, IP reputation, domain reputation etc.) If you have any external gateway, you can try sending emails to gmail through that gateway and check the status.

Regards,

Sharif

ep 3 09:18:15 mail postfix/postscreen: CONNECT from :48332 to :25
Sep 3 09:18:15 mail postfix/postscreen: ALLOWLISTED :48332
Sep 3 09:18:15 mail postfix/smtpd: connect from localhost
Sep 3 09:18:15 mail postfix/smtpd: lost connection after CONNECT from localhost
Sep 3 09:18:15 mail postfix/smtpd: disconnect from localhost commands=0/0
Sep 3 09:18:15 mail postfix/dkimmilter/smtpd: connect from localhost
Sep 3 09:18:15 mail postfix/dkimmilter/smtpd: 5C6A4F27EE9: client=localhost
Sep 3 09:18:15 mail postfix/cleanup: 5C6A4F27EE9: message-id=<SEZPR02MB8523FE8D9D019F3743E1A92CAD932@SEZPR02MB8523.apcprd02.prod.outlook.com>
Sep 3 09:18:15 mail postfix/qmgr: 5C6A4F27EE9: from=<sreehari@phykon.co.in>, size=2415, nrcpt=1 (queue active)
Sep 3 09:18:15 mail postfix/dkimmilter/smtpd: disconnect from localhost ehlo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Sep 3 09:18:15 mail amavis: (1849334-07) z7Qx99VC39c5 FWD from <sreehari@phykon.co.in> -> <sreeandsree19@gmail.com>, BODY=7BIT 250 2.0.0 from MTA(smtp::10030): 250 2.0.0 Ok: queued as 5C6A4F27EE9
Sep 3 09:18:15 mail amavis: (1849334-07) Passed CLEAN {RelayedOutbound}, ORIGINATING LOCAL :28827 <sreehari@phykon.co.in> -> <sreeandsree19@gmail.com>, Queue-ID: 12E1FF25B20, Message-ID: <SEZPR02MB8523FE8D9D019F3743E1A92CAD932@sezpr02mb8523.apcprd02.prod.outlook.com>, mail_id: z7Qx99VC39c5, Hits: -, size: 1975, queued_as: 5C6A4F27EE9, 56 ms
Sep 3 09:18:15 mail postfix/smtp: 12E1FF25B20: to=<sreeandsree19@gmail.com>, relay=127.0.0.1:10026, delay=0.45, delays=0.38/0.01/0/0.05, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp::10030): 250 2.0.0 Ok: queued as 5C6A4F27EE9)
Sep 3 09:18:15 mail postfix/qmgr: 12E1FF25B20: removed
Sep 3 09:18:15 mail postfix/amavisd/smtpd: connect from localhost
Sep 3 09:18:15 mail postfix/amavisd/smtpd: Anonymous TLS connection established from localhost: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256
Sep 3 09:18:15 mail postfix/amavisd/smtpd: 64E1BF25B20: client=localhost
Sep 3 09:18:15 mail postfix/cleanup: 64E1BF25B20: message-id=<SEZPR02MB8523FE8D9D019F3743E1A92CAD932@SEZPR02MB8523.apcprd02.prod.outlook.com>
Sep 3 09:18:15 mail postfix/smtps/smtpd: disconnect from unknown ehlo=1 auth=1 mail=1 rcpt=1 data=1 quit=1 commands=6
Sep 3 09:18:15 mail postfix/qmgr: 64E1BF25B20: from=<sreehari@phykon.co.in>, size=3402, nrcpt=1 (queue active)
Sep 3 09:18:15 mail postfix/amavisd/smtpd: disconnect from localhost ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7
Sep 3 09:18:15 mail postfix/smtp: 5C6A4F27EE9: to=<sreeandsree19@gmail.com>, relay=127.0.0.1:10025, delay=0.07, delays=0.01/0.01/0.01/0.03, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 64E1BF25B20)
Sep 3 09:18:15 mail postfix/qmgr: 5C6A4F27EE9: removed
Sep 3 09:18:15 mail postfix/smtp: warning: DNSSEC validation may be unavailable
Sep 3 09:18:15 mail postfix/smtp: warning: reason: dnssec_probe 'ns:.' received a response that is not DNSSEC validated
Sep 3 09:18:17 mail postfix/smtp: 64E1BF25B20: to=<sreeandsree19@gmail.com>, relay=gmail-smtp-in.l.google.com:25, delay=2.2, delays=0.03/0/1.5/0.61, dsn=2.0.0, status=sent (250 Queued id=0x2000dc7f)
Sep 3 09:18:17 mail postfix/qmgr: 64E1BF25B20: removed
Sep 3 09:18:18 mail saslauthd: zmauth: authenticating against elected url 'https://mail.phykon.co.in:7073/service/admin/soap/' ...
Sep 3 09:18:18 mail saslauthd: zmpost: url='https://mail.phykon.co.in:7073/service/admin/soap/' returned buffer->data='<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"><soap:Header><context xmlns="urn:zimbra"/></soap:Header><soap:Body><soap:Fault><soap:Code><soap:Value>soap:Sender</soap:Value></soap:Code><soap:Reason><soap:Text>authentication failed for </soap:Text></soap:Reason><soap:Detail><Error xmlns="urn:zimbra"><Code>account.AUTH_FAILED</Code><Trace>qtp532677950-897522:1725355098674:fc4d927c244e7c80</Trace></Error></soap:Detail></soap:Fault></soap:Body></soap:Envelope>', hti->error=''
Sep 3 09:18:18 mail saslauthd: auth_zimbra: mysqladmin@co.in auth failed: authentication failed for
Sep 3 09:18:18 mail saslauthd: : auth failure:
Sep 3 09:18:18 mail postfix/smtps/smtpd: warning: unknown: SASL LOGIN authentication failed: authentication failure, sasl_username=mysqladmin@co.in
Sep 3 09:18:19 mail postfix/postscreen: CONNECT from :52986 to :25
Sep 3 09:18:19 mail postfix/postscreen: ALLOWLISTED :52986
Sep 3 09:18:19 mail postfix/smtpd: connect from _gateway
Sep 3 09:18:19 mail postfix/smtpd: NOQUEUE: filter: RCPT from _gateway: <>: Sender address triggers FILTER smtp-amavis::10026; from=<> to=<sreehari@phykon.co.in> proto=SMTP helo=<Sophos>
Sep 3 09:18:19 mail postfix/smtpd: 103A7F25B20: client=_gateway
Sep 3 09:18:19 mail postfix/cleanup: 103A7F25B20: message-id=<20240903091819.103A7F25B20@mail.phykon.co.in>
Sep 3 09:18:19 mail postfix/qmgr: 103A7F25B20: from=<>, size=4383, nrcpt=2 (queue active)
Sep 3 09:18:19 mail postfix/smtpd: disconnect from _gateway helo=1 mail=1 rcpt=1 data=1 quit=1 commands=5
Sep 3 09:18:19 mail amavis: (1850769-07) ESMTP :10026 /opt/zextras/data/amavisd/tmp/amavis-20240903T072510-1850769-Q29Ia03O: <> -> <sreehari@phykon.co.in>,<sreehari@phykon.com> Received: from mail.phykon.co.in () by localhost (mail.phykon.co.in ) (amavis, port 10026) with ESMTP; Tue, 3 Sep 2024 09:18:19 +0000 (UTC)
Sep 3 09:18:19 mail amavis: (1850769-07) Checking: UjKgxtH6NUDu ORIGINATING/MYNETS <> -> <sreehari@phykon.co.in>,<sreehari@phykon.com>
Sep 3 09:18:19 mail amavis: (1850769-07) WARN: MIME::Parser error: part did not end with expected boundary; ; error: unexpected end of parts before epilogue
Sep 3 09:18:19 mail amavis: (1850769-07) local delivery: <> -> bad-header-quarantine, mbx=/opt/zextras/data/amavisd/quarantine/badh-UjKgxtH6NUDu
Sep 3 09:18:19 mail postfix/dkimmilter/smtpd: connect from localhost
Sep 3 09:18:19 mail postfix/dkimmilter/smtpd: 19C2BF28101: client=localhost
Sep 3 09:18:19 mail postfix/cleanup: 19C2BF28101: message-id=<20240903091819.103A7F25B20@mail.phykon.co.in>
Sep 3 09:18:19 mail opendkim: 19C2BF28101: can't parse From: header value ' '
Sep 3 09:18:19 mail postfix/dkimmilter/smtpd: disconnect from localhost ehlo=1 mail=1 rcpt=2 data=1 quit=1 commands=6
Sep 3 09:18:19 mail postfix/qmgr: 19C2BF28101: from=<>, size=4898, nrcpt=2 (queue active)
Sep 3 09:18:19 mail postfix/amavisd/smtpd: connect from localhost
Sep 3 09:18:19 mail amavis: (1850769-07) UjKgxtH6NUDu FWD from <> -> <sreehari@phykon.co.in>,<sreehari@phykon.com>, BODY=7BIT 250 2.0.0 from MTA(smtp::10030): 250 2.0.0 Ok: queued as 19C2BF28101
Sep 3 09:18:19 mail postfix/amavisd/smtpd: Anonymous TLS connection established from localhost: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256
Sep 3 09:18:19 mail postfix/amavisd/smtpd: 1C42DF28106: client=localhost
Sep 3 09:18:19 mail postfix/cleanup: 1C42DF28106: message-id=<20240903091819.103A7F25B20@mail.phykon.co.in>
Sep 3 09:18:19 mail postfix/amavisd/smtpd: disconnect from localhost ehlo=2 starttls=1 mail=1 rcpt=2 data=1 quit=1 commands=8
Sep 3 09:18:19 mail postfix/smtp: 19C2BF28101: to=<sreehari@phykon.co.in>, relay=127.0.0.1:10025, delay=0.02, delays=0.01/0/0/0, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 1C42DF28106)
Sep 3 09:18:19 mail postfix/smtp: 19C2BF28101: to=<sreehari@phykon.com>, relay=127.0.0.1:10025, delay=0.02, delays=0.01/0/0/0, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 1C42DF28106)
Sep 3 09:18:19 mail postfix/qmgr: 1C42DF28106: from=<>, size=5289, nrcpt=2 (queue active)
Sep 3 09:18:19 mail amavis: (1850769-07) Passed BAD-HEADER-1 {RelayedInternal,RelayedOutbound,Quarantined}, ORIGINATING/MYNETS LOCAL :52986 <> -> <sreehari@phykon.co.in>,<sreehari@phykon.com>, quarantine: badh-UjKgxtH6NUDu, Queue-ID: 103A7F25B20, Message-ID: <20240903091819.103A7F25B20@mail.phykon.co.in>, mail_id: UjKgxtH6NUDu, Hits: -, size: 4339, queued_as: 19C2BF28101, 46 ms
Sep 3 09:18:19 mail postfix/smtp: 103A7F25B20: to=<sreehari@phykon.co.in>, relay=127.0.0.1:10026, delay=0.06, delays=0.01/0/0/0.04, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp::10030): 250 2.0.0 Ok: queued as 19C2BF28101)
Sep 3 09:18:19 mail postfix/smtp: 103A7F25B20: to=<sreehari@phykon.com>, orig_to=<sreehari@phykon.co.in>, relay=127.0.0.1:10026, delay=0.06, delays=0.01/0/0/0.04, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp::10030): 250 2.0.0 Ok: queued as 19C2BF28101)
Sep 3 09:18:19 mail postfix/qmgr: 19C2BF28101: removed
Sep 3 09:18:19 mail postfix/qmgr: 103A7F25B20: removed
Sep 3 09:18:19 mail postfix/lmtp: 1C42DF28106: to=<sreehari@phykon.co.in>, relay=mail.phykon.co.in:7025, delay=0.07, delays=0/0.01/0/0.05, dsn=2.1.5, status=sent (250 2.1.5 Delivery OK)
Sep 3 09:18:21 mail postfix/smtp: 1C42DF28106: to=<sreehari@phykon.com>, relay=smtp.google.com:25, delay=2.1, delays=0/0/1.6/0.51, dsn=2.0.0, status=sent (250 Queued id=0x2000dc81)
Sep 3 09:18:21 mail postfix/qmgr: 1C42DF28106: removed

Hi,

Still I believe the gmail bounce back is from gmail end. May be if possible, just share the log from /var/log/carbonio.log and the complete header of the bounce back message.

Regards,

Sharif

seems like the problem is 

- Invalid DNS and reverse DNS lookup

- No properly DMARC is configure in DNS/domain provider

have you validate your mail domain using mxtoolbox.

I checked all the DNS records and they are published properly I checked Google Postmaster tools, no error in it.

The error message 550 5.7.1 with the link to Google's support page indicates that the email you are trying to send has been rejected by Google's mail servers because it was identified as potentially unsolicited or spam.

Could please make sure that SPF, DKIM, DMARC, PTR records for your domains are published properly and try again?

sreeandsree19@gmail.com - 550 5.7.1  https://support.google.com/mail/?p=UnsolicitedMessageError  41be03b00d2f7-7d4cbe0bf2asi2862528a12.642 - gsmtp

Also, when you are managing an email server, I would suggest to take help of https://postmaster.google.com/ tool of Google to monitor your server/IP reputation.

Regards,

Sharif