dovecot - Apr 2020 - Fwd: Load balancer for dovecot servers - Not able to send emails

Hi All,

I need your help on one of the issue in Dovecot.

I have the dovecot version 2.0.9 installed on RHEL linux 6.10 version. It's
a single/standalone Live server.

Now I have created another server with the same configuration for the
resilince purpose. I also tested and I am able to send the emails to both
of the dovecot servers separately/individually. They are working fine.

Now I have added those two servers under a F5 load balancer and created a
FQDN (example: testing.test.com). I changed the rules to send the traffic
to FQDN "testing.test.com", where it should redirect the email to one
of
those 2 servers.

When I sent the email to FQDN "testing.test.com", I am getting the
below
error.

pf1_inbd/smtp[30292]: 66A5F5F6: to=<xxxxx at yyy.com>,
relay=testing.test.com[xxx.xxx.xxx.xxx]:25,
delay=13, delays=0.09/0.08/13/0, dsn=4.4.2, status=deferred (lost
connection with testing.test.com [xxx.xxx.xxx.xxx] while receiving the
initial server greeting)

Could you please let me know how to fix this issue? It's a great help for
me.

Thanks & Regards,
Kishore Potnuru
>
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>>>>> "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

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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