Have they worked before or is the first time you are using the product ?

Hi Toad-Hall, and thanks for responding.

I had previously run it (half an hour earlier) on a folder with about 5,000 messages. It seemed to work OK, finding about 700 dupes.

Obviously with that number involved it would be a nightmare to have to go and check if all dupes were found, so I have to "believe" the software.

Since then it has not worked at all, and I am directing it to a range of folders, each with only about 20-50 messages, which is how I know it is missing them all.

I know one of the folders has about a 50% dupe content.

Ian

You should always contact the author of the affected addon

I prefer to ask the Community as (a) they are then aware of a possible problem, and (b) (from past experience) they are more likely to have an answer or to offer an alternative than an Author. Besides, surely an Author is part of the Community too?

IanGreen said

Besides, surely an Author is part of the Community too?

No, most are not part of the active Thunderbirdcommunity. And even more important with regard to your (incorrect) assumption, highly unlikely to be part of the generic _support_ community in which you just posted.

And lastly, look at the addon's pages like https://addons.mozilla.org/en-US/thunderbird/addon/remove-duplicate-messages-alte/ and you will see every one has an explicit support link stated that I have no doubt the author prefers you use.

I can also tell you that the authors of both addons you mention are not part of the active communty and are certainly not to be found here in this support forum.