Older versions: https://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/

Updating: Tools|Options|Advanced|Update

Thank you for this quick reply.

Unfortunately, I don't know the version number of my previous Thunderbird. So I will revert to version 24.5.0 which was the version I first used. I have stopped version 38 from updating itself. However, I'm a little nervous about uninstalling version 38 in case this loses all my emails. On the other hand will downloading version 24.5.0 and using it alongside version 38 work, or will that damage my emails? Can you or anyone else advise on the best process of reversion?

The web siter says mail merge wi=orks with V38 https://addons.mozilla.org/en-US/thunderbird/addon/mail-merge/?src=ss so perhaps doing anything is more than you need to do.

Thanks Matt.

When I followed your link I noticed that the current version of the add-on works for Thunderbird 31 or later, so I can't revert to Thunderbird 24.5.0.

But despite it's claim to work in Thunderbird 38 the add-on doesn't work for me. There is more than one way to use it and I am using Address Book mode. The dialogue no longer offers a choice of HTML/Text/Both. On exit from the dialogue the software says it is attaching and a timer runs forever. I'll report the bug but first I need to send 450 oversue emails!

please email the author here myaddons@gmx.de

Based on the comments on the page, it clearly works with V38. Although there are some issues with HTML it would appear.

If you don't get a fast response from the author please post back and we will see what can be done.

I know it does not help you. But I do my mail merge using Libre office and if sends the mail for me. No Thunderbird. Using and IMAP account means that the mail added to the sent folder by Outlook.com and Gmail syncs back to Thunderbird after the event.

The previous version of Thunderbird was 31. So you can still downgrade. But note you may have to remove add-ons and add them again. Lightening will be a for sure as the downgrade does not downgrade add-ons.

Thanks again Matt.

I will email the author as you suggest rather than raise a bug report. But there is no way he can fix this in time for me to get my emails out so I will revert to Thunderbird 31.

I use LibreOffice but don't understand the technicalities of your method so I think reverting to Thunderbird 31 is best for me.

Now it's 2am in London so I must sleep. I will post here both the response from the author and the success or otherwise of reverting to Thunderbird 31.

I contacted the author of the add-on and he has now fixed the problem and updated the add-on to include the fix. So I will not revert to an earlier version of Thunderbird. I will, however, continue to prevent Thunderbird from updating automatically.

This probelm is now solved for me. Thank you to everyone who contributed a reply.