Thanks for the replies. Have updated her Thunderbird to 31.1 - I always thought that it updated automatically in the past. Edit - 'Automatically install updates'
is ticked in Thunderbird 'Tools-Options-Advanced-Update', as it is on my computer and neither has updated automatically since version 24.6.
I should have investigated more thoroughly before posting the query although it had me beaten at the time I did post. It's all sorted now
- when I right clicked 'Properties' on the contact in Address Book the 'Always Prefer Display Name Over Message Header' was ticked (default setting) and goodness knows how but she had the other company's email address inserted as the Display Name. She has no idea how that happened.
