You didn't tell us anything about the account. If this is IMAP, you can delete individual messages, and if POP, the messages would generally have already been downloaded. From your post, I infer that your wife has her account separate from yours, but that you still see her messages? Please clarify. Another option is to sign in online and delete from there.

Thanks for your response! Thunderbird lists all my email accounts. Mine is an imap account, my wife's is pop. They are both from the same local email provider. That probably explains why whenever I click on it Thunderbird wants to download all 18000+ messages but that of course is time consuming and never gets completed. I am currently in a remote location with only my Verizon connection and only 2 bars lte of signal. It's very slow! Some of those messages are current as she's actively using the account so they don't all want to be deleted -- but most of them do. Suggestions?

It isn't clear the final objective. Does she have the account on a separate computer? If so, why is her account on your PC? Is she wanting messages deleted, or just you? My concern is that in helping you, we also affect the account as she uses it. A better understanding of your intent on deleting some of her messages but not all, as I would normally assume she manages that. If there are 18,000 messages there, my assumption is that she wants them there. My inference is that you just added her account to your PC for the purpose of removing some messages for her. True? If that is the situation, then I suggest you create an IMAP version of her account on your PC so you can selective delete messages.

There has been no problem with this for a very long time. There was a recent update to Thunderbird and after that update it started wanting to download those 18000 messages on my computer. I think I see her stuff because it's all shared on the cloud. In any case I don't know why all of a sudden it wants to download all those messages and it ties up the system trying to do this. This is especially bad right now as I'm 1000 miles from home and depending on my Verizon connection for internet access and it's only 1 -2 bars lte and extremely slow.

Ok, I do not understand why you have her POP account on your computer. That's the only reason you see her messages. To stop attempts to download, try this: - click account settings for her account and UNtick the 'check for new messages at startup' - the safest way would be also to click settings>privacy&security, click 'saved passwords' and 'show passwords' and then rightclick on her account's incoming server and delete password.

If you want to delete some of her messages, you should either use your online account or set up an IMAP account for her messages.