KMail imap connection broken by openssl update [SOLVED]

[Andy G Wood <agw@bas.ac.uk>]

Just in case somebody is helped by this .....

After a recent openssl (1.1.1-2) update in Buster, one of my KMail connections 
to an internal imap server stopped working (symptoms: could not retrieve old 
emails and could not view any "Folder Properties" in that account).

I was half expecting this, and the fix was in the description of the update 
from the package maintainer:
------
Following various security recommendations, the default minimum TLS version 
has been changed from TLSv1 to TLSv1.2. Mozilla, Microsoft, Google and Apple 
plan to do same around March 2020.
[...]
Changing back the defaults in /etc/ssl/openssl.cnf to previous system wide 
defaults can be done using:
   MinProtocol = None
   CipherString = DEFAULT
It's recommended that you contact the remote site in case the defaults cause 
problems.
------

Andy.