Emails Not Delivering | PHP Mail Not Working | Time Out Errors

Hi Team,

Moved from cPanel to CWP recently. Setup CWP on Linode.

PHP emails are working and in the queue, but I am getting timeout errors.

For example, timeout errors on Google lookup:
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connect to alt2.aspmx.l.google.com[2607:f8b0:4023:c0b::1a]:25: Connection timed out
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More logs:
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Jun 24 06:01:41 dev postfix/smtp[4120]: connect to aspmx.l.google.com[2404:6800:4003:c02::1a]:25: Connection timed out
Jun 24 06:01:41 dev postfix/smtp[4142]: connect to aspmx.l.google.com[2404:6800:4003:c02::1a]:25: Connection timed out
Jun 24 06:01:44 dev postfix/smtp[3885]: connect to alt2.aspmx.l.google.com[142.250.141.27]:25: Connection timed out
Jun 24 06:02:11 dev postfix/smtp[4120]: connect to alt2.aspmx.l.google.com[142.250.141.27]:25: Connection timed out
Jun 24 06:02:11 dev postfix/smtp[4142]: connect to alt1.aspmx.l.google.com[173.194.202.26]:25: Connection timed out
Jun 24 06:02:14 dev postfix/smtp[3885]: connect to alt2.aspmx.l.google.com[2607:f8b0:4023:c0b::1a]:25: Connection timed out
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I've updated the DNS to be CloudFlare followed by Google with no luck.

Not sure if it is possible a firewall issue? Seems like Port 25 is being blocked and timing out? I don't have any restrictions on Port 25 at this stage.......

Any tips would be great or if you need any other logs.

Thanks.

http://forum.centos-webpanel.com/index.php?topic=10765.msg37109#msg37109 - This could be the issue since moving Linode.

I have submitted a ticket with them.

Got Linode to unblock the ports and good to go!