Kmail distortion of headings from recent Thunderbird messages.

Hi all, When reading messages in Kmail sent to me by (2) correspondents using Thunderbird (v38), the FROM and the TO fields of the messages are not correctly represented: the French accents in the sender's real name and in the real names in the recipient list are distorted. For example, René becomes Renc3a9. This is quite annoying when I want to reply to a list with many names with French accents. This problem does not apply to the body of message, where all accents are ok. I noticed that the problem started on August 30 where i also noticed the two correspondents upgraded to version 38 of Thunderbird for windoze. Earlier messages are ok. I have been using Kmail on my desktop computer for many years without any problems. It is the current version (1.9.10) supplied by Trinity. I use Ubuntu Precise with Trinity R 14.0.2. I tried changing character settings in 'appearance' within Kmail preferences in various combinations, with utf-8 and iso-8859-1 to no avail. Is this something that I need to set correctly in Kmail or something wrong with Tbird? My wife can read those same headings fine on her laptop using Tbird. Any ideas? Marco