hostname in director_mail_servers setting

[k v]

director_mail_servers setting uses IP Adresses as values https://doc.dovecot.org/settings/core/#core_setting-director_mail_servers
As described in the documentation, hostnames are converted to addresses when the configuration is read https://doc.dovecot.org/settings/types/#ip-addresses

This is acceptable in host or virtual machine environment, but becomes a problem in a containerized environment. When any backend container is restarted, its address will change and users related to this backend can no longer connect, but backend (available with new IP address) can process request
for example,
director_mail_servers = dovecot-1 dovecot-2 dovecot-3
becomes in runtime (with one successfully connectetd user foo at example.com)

doveadm director status
mail server ip  tag     vhosts  state   state changed   users
10.0.71.3               100     up      -       0
10.0.71.4               100     up      -       1
10.0.71.5               100     up      -       0

where
dovecot-1 10.0.71.3, dovecot-2 10.0.71.4, dovecot-3 10.0.71.5

When dovevecot-2 backend container restarts, and becomes new IP address, user can't connect to related backend:
imap-login: Info: proxy(foo at example.com,10.0.71.4:143): Started proxying to <10.0.71.4> (<dovecot-2>) (0.009 secs)
imap-login: Error: proxy(foo at example.com,10.0.71.4:143): connect(10.0.71.4, 143) failed: No route to host (after 28 secs, 3 reconnects, local=10.0.71.13:41066)

My suggestion to developers: resolve backend hostnames to IP address on every request to director_mail_servers

It's not about dovemon service with active health checks from dovecot pro, just dynamic hostname resolve
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