Dovecot Load balancing - Please Please Please help me

[Alexander Dalloz]

Am 16.01.2020 um 18:04 schrieb Kishore Potnuru:
>    I need your help on my issue very badly.
> 
> I have the dovecot version 2.0.9 installed on RHEL linux 6.10 version. It's
> a single Live server. I need to add a load balancer by adding another
> server for resilience.
> 
> I cannot upgrade the dovecot version at this time as it is a single live
> server. If something goes wrong, I will be in trouble.
> 
> Basically the requirement/issue is:
> 
> a) it's a single live dovecot POP3/IMAP server
> b) people are accessing their emails from microsoft outlook (by giving the
> same server name as IMAP and SMTP server). But more than 100000 emails will
> be travelled/routed.
> c) This server is not rebooted from couple of years.
> d) Now they are worried about, just in case if the server is having any
> issues during the reboot
>                or
>     if something goes wrong with the server in any case, there will be huge
> issues.
> 
> e) They would like to create resilience by adding another server and emails
> will be travelled from both the servers. If one server is having any issues
> due to any technical issue and if it doesn't come back easily, then the
> emails will be travelled through the other server and there will no
> disturbance to the emails. atleast it travels from the other server.
> 
> I have very less knowledge on this. Could you please help me providing the
> best solution for this.
> 
> I will wait for your reply. Please please please help me.
> 
> Thanks,
> Kishore Potnuru

Don't take it personal Kishore, you probably just inherited that disaster.

RHEL 6.10 is really old and thus your dovecot version ancient and 
unsupported by upstream. RHEL 6.10 is going EOL by end of Nov this year. 
And I am not sure that system is really a clean 6.10 if it hasn't been 
rebooted since several years as you state.

Load balancing will not solve your issue. Migrate away from that host to 
a fresh new install with a more current OS and dovecot release. Spin up 
the new system, configure dovecot properly, sync the mail over from the 
old system to the new one. Plan a maintenance downtime where you do a 
final sync and then replace the old host with the new one which you give 
the same identity. The downtime will be minimal.

Alexander