I don’t like thunderbird too much, very cluttered interface
However lots of things are possible , but it requires to figure a lot of things out and configure them properly

profile

re-install TB, keep profile

• make sure you have copied / backuped the thunderbird profile data
• launch Thunderbird , this will create .thunderbird in /home
• delete the profile folder(s)
• adapt the profile & ini files to point to the existing thunderbird profile

use multiple profiles

Profile Manager is not displayed by default.
==> start Thunderbird with a switch that makes the Profile Manager appear: ( terminal ) thunderbird -ProfileManager

acount settings

mail account pasword has changed

menu > preferences > Privacy & Security > Passwords > Saved Passwords > Click Show Passwords > Right click password > Edit
( obsolete : tools > Options > Security > )

cleanup accounts

• remove all old entries
• recheck / refresh mail
  if not ok : restart TB
  if still not ok , remove last pasword entry as wel & re-enter account info

https://www.freebsd.org/cgi/man.cgi?query=readpst&sektion=1&apropos=0&manpath=FreeBSD%2B10.2-RELEASE%2Band%2BPorts