I’ve been using Thunderbird as a POP3 mail client. It is set to delete downloaded mail from my Hotmail account. Lately I’ve been downloading 2 copies of some mail from Hotmail into Thunderbird. How can I stop this redundancy?
You will have to log into windows live / outlook / hotmail with your web browser as Microsoft has changed things. First you have to enable pop in the settings, next you have to tell hotmail that you want you pop mail client (thunderbird) to delete emails after it downloads them or if hot mail should now move those emails to a special folder. Also, you might have more control, if you access hotmail with Imap (but not all hotmail accounts have imap access) Imap keeps all the emails on the server (however thunder bird will still download a copy of the email unless you change that in thunderbird's settings)
From my experience, I have found that even if I use a email client to pick up my mail, I still have to log in with a web browser to check on things and change settings.
Also be aware that hotmail has changed things, so it's worth a web login...
Have you set TB to delete the downloaded messages immediately, or after a number of days? If the latter, then this may be causing the problem (although of course it shouldn't). If the former, then all I can think of is that either you are being sent messages twice (easy to check via webmail, I suppose) or Outlook.com is not working properly.
I guess we need to start with a couple of questions. Are you sure that you weren't sent 2 copies of these emails? If you were, there isn't much you can do. Do you have aliases set up where you are receiving emails on both aliases or have you set up your Hotmail account to retrieve emails from another account? Are you receiving these emails on both aliases or both accounts?