Little problems with serarch in e-mail

[gsup]

Hello.

I have next mail server: Ubuntu 18.04 Lts + iRedmail -1.3.1 ldap + Nginx+php-fpm7.2
This server have about 60 e-mail and some e-mails have about 80k mails.
Problem in next: If any e-mail have about 15-20k mails, and if i try to find something with "search tab", it will tqake about 40-120 seconds, with 80k+ mails it's can't find anything. Any idea what should i do, to speed up search algoritms?

Thank you.

[JohnDoh]

The search is performed by your IMAP server not by Roundcube.