Works properly with some minor problem Rated 5 out of 5 stars

It works properly and I use it successfully since 1 day. My colleagues started using it too.
Today I had a problem. The addon correcly identified many duplicated messages, tagged them for delete, but the the delete process didn't work. I had to close Thunderbird and when I opened it again, the add-on worked smoothly.

It can do like its name, but need more improvement Rated 1 out of 5 stars

Double click can not change the mark "DEL" or " KEEP"

Worked brilliantly Rated 5 out of 5 stars

I was skeptical, but it worked brilliantly. I had to go into the options and set a minimum of variables before it worked for me, but after that it was superb -- very fast and thorough in all stages. Worked great with Gmail IMAP. Allowed me to delete the larger message, an option which the supposedly rewritten "alternate" version doesn't offer.

Problems running this with Thunderbird 45.8.0 on Mac OS X Rated 1 out of 5 stars

I would really like to use this tool, but unfortunately it does not work in my case. I have Thunderbird 45.8.0 on Mac OS X, and approximately 570,000 emails stored. When I try to identify/remove duplicates with this program, I get a message saying that there are more than 200,000 messages, so it is switching to a memory-saving "slow mode". After that, the CPU is pinned and nothing happens. I have waited overnight, but the CPU remains pinned and no duplicates are identified. I tried to find contact information to get in touch with the author, but could not find it.

This was great Rated 3 out of 5 stars

Used to work excellently, but it seems broken now (under 45.7.0).

:(

Good with some few improvements needed - for IMAP use Rated 4 out of 5 stars

Have used this add-on for long time. Previously on POP3 setup not many issues found. Now I am mostly on IMAP setup, with many duplicates.
I have found the following limitations. If you run the search on a multiple folders which results in many duplicates (say more than 1000), then the add-on "crashes". If finds the duplicates, but doesn't actually delete them. Only if the duplicates are around max 500 then the add-on runs without crashing. I think its related to the speed that the IMAP can handle the "actions" coming from Thunderbird.
With current add-on, its best to limit the application to only 1 folder at a time.
Also if duplicates to be deleted are more than 400-500 messages, better to split the folder in more subfolders and ran to each subfolder.
I would like if the add-on could be chosen to ran on "Selected messages", similarly to what is possible with the Filters. This way, we avoid needing to split folders in subfolders with less duplicates.
Other solution, could be to setup the add-on automatically to run on not more that 400-500 messages per time.

Gmail Rated 4 out of 5 stars

When one selects the top folder if using gmail (i.e. the folder containing all the other message folders), then the addon shows duplicates for all/many messages. This is because all/many messages have duplicates on Gmail's server (e.g. in the All Mail or Important folders). It would be good if there was a checkbox to ignore the Gmail (server) folder. This could be in the General Settings tab for Preferences. Also, it would be helpful if the attributes columns for the messages could contain an indicator showing whether an attachment is present on a message. This is because of a fault in Thunderbird for Gmail (and possibly other imap email) which results in there being 2 copies of a message when a message has its attachments detached: one copy is of the original message still containing attachment(s) and the other copy contains the message without attachment(s).

Worked Great for Me Rated 5 out of 5 stars

Effortless to install and run. Accurate. Beats doing it manually.
Thank you.

Worked a treat with TB 47.0.1 Rated 5 out of 5 stars

Tried the newer 'alternate' version which did nothing. This add-on made easy work of deleting dupes that turned up after fixing corruption of my email files.

Resizing the window Rated 3 out of 5 stars

I just wish the developer would still make a small change after all these years: If you have lots of duplicates, it would be nice to get more lines in to "Duplicate Messages" window. Now, if you put that window to full size (on OS X/macOS), the height of the frame containing the messages is unchanged.

It does not delete the messages from the folder Rated 3 out of 5 stars

Hello!
I have searched for hours and could not find a solution for this. I have an IMAP Gmail account, and my "All Mail" folder has 50146 messages. I run the extension and it works fine, it searches and finds about 13000 duplicates. However, when I click to delete the duplicates, it does nothing. I can notice that the number of messages in the folder is still the same (50146).
Is there a reason for this? Is this because the "All Mail" Gmail folder is undeletable, or maybe because the folder is too large?? Please help!!!

Works great and ultra fast too! Rated 5 out of 5 stars

Impressive, the (Alternate) version I tried did nothing. However this add-on functioned exactly as expected -and- the results were instantaneous! HIGHLY RECOMMENDED

BTW, the review below (entitled-"Great with one annoying limitation") is in complete error. This add-on easily lets you choose whether you want to use MessageID for comparison purposes or not.

Saved my biscuits Rated 5 out of 5 stars

I had some massive duplication in two folders. Really bad. I discovered this. Ran into some limitations with T-Bird and how it handles trash. Ran into some slowdowns but, as I said in the title, it save my biscuits, or however you want to say it, it saved the da. I broke the mailboxes down into digestible chunks and than ran this on each one, then reassembled them. Thanks. If it were donation-ware, I'd donate 5 bucks, but I could not find a link.

Great with one annoying limitation Rated 2 out of 5 stars

Unfortunately I have many duplicates that are absolutely identical except for the messageID. THis addon does not allow comparisons of messageID's so is only of limited use to me.

erratum: runs on 45.2 as well Rated 5 out of 5 stars

just tried to run it on 45.2 and it detected duplicates. thanks

This user has a previous review of this add-on.

Great addon. Had one message cause it to hang. Rated 4 out of 5 stars

I used this addon to sort through years of backups to reduce them to a set of email without duplicates. Worked great except: It would hang and I finally found the one message that caused it. I need to submit a file to be checked as to why.

Funktioniert einwandfrei (45.1) Rated 5 out of 5 stars

Mal eben in wenigen Sekunden ein paar 10000 Mails gelöscht. Vielen Dank für dieses praktische Plugin!

great add on ...but Rated 4 out of 5 stars

Work only one time when just installed in 45.1. Does not work when Thunderbird is shut down and reopened. To get it work I have to uninstall the module and process a fresh install on each thunderbird restart, which is a bit tedious ;)

Works faultlessly in Thunderbird 45.1 Rated 5 out of 5 stars

Thanks so much for this, Thorsten.

Does not work with TB 45.0 Rated 4 out of 5 stars

It does not work with Thunderbirt 45.0. Before it works qiute well. Could you make it work again, please?