re :It may be because I have just changed the account settings from "never delete" to "delete messages that are more than a week old" and all of these messages are both unread and months old.

Well if you have those settings then it would explain what is occuring. You said emails must get deleted if over a specified age and so they were deleted.

I'm not sure what your question is? it is not a neat trick, it's simply doing what you asked. Any email detected with an age over XX days will be deleted.

I'm really wondering if this is expected behaviour? Is clicking on the trash folder as mail is downloading always going to redirect mail to trash?

I don't think its because you click on trash but that you shift focus to another folder. As long as you don't open inbox it counts unread mail that enters the folder. when you open inbox it recalculate and gives you the actual number. It may also be that it doesn't run this "filter" until you shift focus to it.

Toad-Hall might know this better, but I think you need to compact your inbox. very soon as the mail ist just being marked as deleted but still resides in the inbox.

A part of my concern is that I could redirect the flow of incoming messages by changing focus or by clicking onto a different folder.

I'm not sure that I was really doing that. It's likely that the account settings were responsible for the messages being deleted and I was confused by that.

I'll have to allow the mail to build up in that account so that I can test it.

Selecting a folder to view has nothing to do with where an email is auto downloaded to , Downloading will be to the Pop mail account Inbox and then any filtering or options to delete will be applied to emails that meet those conditions.

Initially you said; At present I am deleting all the messages in a POP account you also said: changed the account settings from "never delete" to "delete messages that are more than a week old

Please state exactly where you did this. Did you do it here? Tools > Account Settings > Disc Space for the pop mail account Did you select the option: 'Delete messages more than 7 days old' ?

This would have the effect of deleting everything older than a week off BOTH the server and your Thunderbird pop mail account.

then you said: as mail is downloading always going to redirect mail to trash

What you have said and we need to know this.... re: the mail currently downloading from server to pop inbox. Are you currently downloading old mail off server or new mail with a date of today? Are you saying new mail with todays date is downloading, but not appearing in Inbox? If yes, please do this: Right click on 'Inbox' folder and select 'Properties'. Click on 'Repair Folder' button. Click on 'OK' button.

Click on any other folder eg: Sent then reselect 'Inbox' folder.

Please report back on results.

.

Please state exactly where you did this. Did you do it here? Tools > Account Settings > Disc Space for the pop mail account Did you select the option: 'Delete messages more than 7 days old' ?

YES.

Are you currently downloading old mail off server ...?

YES, more than a year old.

Since doing that, new mail the new mail that arrives is not deleted immediately.

It appears as though the filtering was fooling me.