Hi Roger, welcome to the board.
This is part of The Bat! security settings - put simply, it lets you decide which linked images you want to display in your emails. As you may know, some HTML emails have images which are not actually sent with the email, but rather are linked from a remote server. This can be quite innocent, but it can also be used for not so innocent means, such as testing if spam to an email address is read - thus confirms the email address as being live, and therefore you get even more spam as a result.
The Download URL Manager lets you decide which linked emails are displayed on your computer... in earlier versions of TB! these images were just never shown and all you saw was a red x where they should be, but it was realised that some images are wanted, and this gives you the option to decide which is which.
You can also whitelist and blacklist domains automatically, so for instance you can set it to always display images in emails from, e.g. Amazon or eBay, but not to display others without asking, or to always block images from domains which send you spam.
Hope this helps.
