apparmor use with Thunderbird is the culprit - on my system
Disabled use with Thunderbird (sudo aa-disable
/etc/apparmor.d/usr.bin.thunderbird) and now I can attached from any of
my folders and also click on a link to open it.
I had a quick look through but couldn't immediately see why - I do have
another system which didn't have a problem after updating so I will
compare the AA profile files.
Thank you Carsten for your pointers
I must have missed the warning on the changeover from Icedove to
Thunderbird!!!
