Can't send email

Good day,

I hope someone can help.

I can receive email but can't send. Internal sending from one to another email on my server works though.

Have set up SPF, DKIM and DMARC and I get a green light at MX Toolbox. New emails can even be set up in a client like Thunderbird without error.

I have contacted my ISP and they initially said the SMTP port was blocked and opened by them. I tried and still nothing. Then my ISP said port 25 was still blocked and they unblocked it. But still not working.

This is the Mail Queue error message:

Queue reason:
00EBD6248E     1482 Fri Jun 26 13:54:32 

(connect to alt2.gmail-smtp-in.l.google.com[2a00:1450:400b:c00::1a]:25: Connection timed out)
                                       
Here is the server's mail log:

Jun 26 13:54:33 mail postfix/qmgr[8042]: 871CB62373: removed
Jun 26 13:55:03 mail postfix/smtp[8378]: connect to gmail-smtp-in.l.google.com[2607:f8b0:400d:c0f::1b]:25: Connection timed out
Jun 26 13:55:33 mail postfix/smtp[8378]: connect to gmail-smtp-in.l.google.com[172.217.197.27]:25: Connection timed out
Jun 26 13:56:03 mail postfix/smtp[8378]: connect to alt1.gmail-smtp-in.l.google.com[2800:3f0:4003:c00::1b]:25: Connection timed out
Jun 26 13:56:33 mail postfix/smtp[8378]: connect to alt1.gmail-smtp-in.l.google.com[64.233.186.27]:25: Connection timed out
Jun 26 13:57:03 mail postfix/smtp[8378]: connect to alt2.gmail-smtp-in.l.google.com[2a00:1450:400b:c00::1b]:25: Connection timed out
Jun 26 13:57:03 mail postfix/smtp[8378]: 00EBD6248E: to=, relay=none, delay=150, delays=0.06/0.03/150/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[2a00:1450:400b:c00::1b]:25: Connection timed out)
Jun 26 13:59:33 mail postfix/smtpd[8375]: timeout after END-OF-MESSAGE from unknown[127.0.0.1]
Jun 26 13:59:33 mail postfix/smtpd[8375]: disconnect from unknown[127.0.0.1] ehlo=1 mail=1 rcpt=1 data=1 commands=4
Jun 26 14:04:30 mail clamd[7911]: SelfCheck: Database status OK.
Jun 26 14:06:41 mail postfix/qmgr[8042]: 00EBD6248E: from=, size=1482, nrcpt=1 (queue active)
Jun 26 14:07:11 mail postfix/smtp[9791]: connect to gmail-smtp-in.l.google.com[2607:f8b0:400d:c0f::1a]:25: Connection timed out
Jun 26 14:07:41 mail postfix/smtp[9791]: connect to gmail-smtp-in.l.google.com[172.217.197.27]:25: Connection timed out
Jun 26 14:08:11 mail postfix/smtp[9791]: connect to alt1.gmail-smtp-in.l.google.com[2800:3f0:4003:c00::1a]:25: Connection timed out
Jun 26 14:08:41 mail postfix/smtp[9791]: connect to alt1.gmail-smtp-in.l.google.com[64.233.186.27]:25: Connection timed out
Jun 26 14:09:11 mail postfix/smtp[9791]: connect to alt2.gmail-smtp-in.l.google.com[2a00:1450:400b:c00::1a]:25: Connection timed out
Jun 26 14:09:11 mail postfix/smtp[9791]: 00EBD6248E: to=, relay=none, delay=879, delays=728/0.05/150/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[2a00:1450:400b:c00::1a]:25: Connection timed out)
Jun 26 14:14:31 mail clamd[7911]: SelfCheck: Database status OK.
Jun 26 14:14:56 mail postfix/smtpd[10648]: connect from unknown[193.56.28.159]
Jun 26 14:14:59 mail postfix/smtpd[10648]: warning: unknown[193.56.28.159]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Jun 26 14:15:05 mail postfix/smtpd[10648]: warning: unknown[193.56.28.159]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Jun 26 14:15:15 mail postfix/smtpd[10648]: warning: unknown[193.56.28.159]: SASL LOGIN authentication failed: UGFzc3dvcmQ6
Jun 26 14:15:25 mail postfix/smtpd[10648]: warning: unknown[193.56.28.159]: SASL LOGIN authentication failed: Connection lost to authentication server
Jun 26 14:15:25 mail postfix/smtpd[10648]: disconnect from unknown[193.56.28.159] ehlo=1 auth=0/4 rset=4 quit=1 commands=6/10

Thanks for your help.

Hai
I had similar issues, initially when I installed CWP its works later when I started to restrict the firewall ports its been block.
I found that I have to open a TCP Outgoing port 25 for my server to send out email to other email server, specially.

I found following in Internet.
SMTP servers send mails between each other on port 25. ISP's block the outgoing port 25 to stop spam and this is now almost "an industry standard". Port 465 and 587 should be used for client - server connections only, so 99% of SMTP servers which will send mails to your server will do it on port 25. As you have changed the port from 25 to 465, they won't be able to connect to your server.

Opened TCP \ UDP ports
TCP IN: 80, 443, 2031, 2083, 49226
TCP OUT: 20, 21, 22, 53, 80, 443, 587, 25
UDP IN:
UDP OUT: 20, 21, 53, 123
I only enabled above ports in the firewall.

and I also disable startup and stop services 'Dovecot IMAP/POP3 Server'  and 'OpenDKIM'.
only enable 'Postfix Mail Server' service.

My intention just to CWP alert email to reach my gmail address for alert & notification. I'm not running any email service for my domains in the server.

Thank you
Regards
Elil