Kmail won't download email

Our law firm has used kmail for many years and supports kde.  My secretary's 
kmail won't work and produces error messages, including:


Unable to store downloaded emails.
Failed to append item.


She uses Debian buster.  Our IT guy (who is familiar with linux) has spent two days 
trying to fix it without success.


I would be most appreciate if someone on this list could help us and happy to wire 
a reasonable fee for his or her time.


My phone is 775-322-8000.  It is now 2:44 pm, Reno Nevada USA time.  We are 
here from 8 am until 5 pm Reno time.


John A. White, Jr.
White Law Chartered
335 W 1st St
Reno, NV 89503