'Menu icon' > 'Options' > 'Options' > 'Attachments' > 'Incoming' content type: Adobe acrobat Document (application pdf) Select the correct 'Action': eg: Use Adobe Reader (default) click on OK

I hadn't thought about changing this setting as it is 'Incoming' rather than 'Outgoing'. My current 'Action' was 'Use Expert PDF' and although Adobe Acrobat wasn't listed as an option to use I changed it to another pdf viewer and it was problem solved. So thanks for your help Toad-Hall. In time I will look at the settings within Expert pdf as I still like to use that.

I am having the same problem. I changed the pdf reader to the adobe but it did not work there. I use Netaddress as my main email address and then forward the mail to Thunderbird. It opens ok in Netaddress but not in Thunderbird and if I save it with Thunderbird and try to open the saved version it will not open. Something in Thunderbird is corrupting it.