Fwd: Load balancer for dovecot servers - Not able to send emails

[Kishore Potnuru]

Hi John,

Thank you for the reply.  Actually it was setup like this by another
member, who left the team/company recently. Now it came to me to handle
that responsibility. That's how I got in to this. At present I am not able
to migrate/upgrade immediately. Because it sends emails around 100K+ emails
everyday and I do not want to disturb that.

Coming back to your question, Actually the connection is :

O365/Outlook >> SMTP Gateway Server >> testing.test.com >> 2 POP3 servers.

Actually "testing.test.com", that is FQDN  name set in F5 load balancer,
where it is having the 2 POP3 servers to route the emails.
When the email was sent from Outlook/O365, first it goes to SMTP Gateway
Server. Now the SMTP Gateway server has the postfix rule to send it to "
testing.test.com". In this location, I am getting the error in SMTP Gateway
Server, where it is not able connect ( lost connection with
testing.test.com [xxx.xxx.xxx.xxx]
while receiving the initial server greeting).

In SMTP Gateway server, instead of "testing.test.com", if i give the
name/ip of any POP3 server, then email delivery is happening successfully
to that POP3 server. The above error is coming only when i use the fqdn "
testing.test.com", instead of direct POP3 server.

Please let me know if you need any more details. Could you please help me
here.

Thanks,
Kishore Potnuru

On Thu, Apr 23, 2020 at 7:13 PM John Stoffel <john at stoffel.org> wrote:

> >>>>> "Kishore" == Kishore Potnuru <kishore.reachme at gmail.com> writes:
>
> Kishore> I have the dovecot version 2.0.9 installed on RHEL linux 6.10
> Kishore> version. It's a single/standalone Live server.
>
> You should really upgradr your setup.
>
> Kishore> Now I have created another server with the same configuration
> Kishore> for the resilince purpose. I also tested and I am able to
> Kishore> send the emails to both of the dovecot servers
> Kishore> separately/individually.  They are working fine.
>
> Dovecot doesn't do the mailing between systems, so i assume you've got
> postfix configured?  And do you have shared storage behind your two
> dovecot instances so that your users don't have to login to multiple
> systems to get emails?
>
> Did you read the docs at:
>
>   https://doc.dovecot.org/admin_manual/dovecot_cluster_architecture/
>
> Kishore> Now I have added those two servers under a F5 load balancer
> Kishore> and created a FQDN (example: testing.test.com). I changed the
> Kishore> rules to send the traffic to FQDN "testing.test.com", where
> Kishore> it should redirect the email to one of those 2 servers.
>
> So how is your F5 configured to work when one server is down?
>
> Kishore> When I sent the email to FQDN "testing.test.com", I am getting
> the below error.
>
> Kishore> pf1_inbd/smtp[30292]: 66A5F5F6: to=<xxxxx at yyy.com>,
> Kishore> relay=testing.test.com[xxx.xxx.xxx.xxx]:25, delay=13,
> Kishore> delays=0.09/0.08/13/0, dsn=4.4.2, status=deferred (lost
> Kishore> connection with testing.test.com [xxx.xxx.xxx.xxx] while
> Kishore> receiving the initial server greeting)
>
> Kishore> Could you please let me know how to fix this issue? It's a great
> help for me.
>
> Sounds like you haven't actually setup your system correctly.  But
> we're not going to be able to help until you provide more details.
> It's also not clear from the about log file *which* server gave you
> this error.
>
> It would be smarted to start from scratch with an upto date install of
> dovecot (and postfix in my opinion) according to the Dovecot docs
> above, and test that out in a test environment.  Then you would use
> 'doveadm' sync to migrate user accounts over to the new system.
>
> John
>
>
>
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