In the left column of folders right click Trash. The select Properties. Select the tab Retention Policy. Uncheck the box if checked. Select the number of days you wish to retain before deletion.

Thank you crpendergrass. Sorry for the time delay but much appreciated. Fixed the problem.

Changing the retention policy on my e-mail folders works for all folders except Trash. I cannot change it at all so it is emptying trash every day. Please help.

Normally you would... Right click on "Trash" folder in left column of Thunderbird window. In the "Folder Properties" window select the second tab "Retention Policy." If you want the same settings as your mail client (ie. Gmail, etc.), check the box accordingly. If you want something else, uncheck the box and adjust the settings.

It sounds like you might have a bug in your Thunderbird installation. Perhaps you should try to install or reinstall the latest version.

That thought had occurred to me since I only have the problem with trash. Thanks for the advice. I will try installing the latest version.