Evidently, you are asking about the Windows Mail app.  It is thoroughly disliked by so many people that I don't know if you will get an answer.  I recommend Thunderbird Portable.

Aside from that, I'm not sure what you are describing.  The program is set by default to download images in e-mails and you say it always says downloading.  Perhaps you need to change the setting for when it downloads.  I played with the app and there is a setting so the app will only download when you issue the download command, f9.  The default setting, as I recall, is that it downloads based on your pattern of use, in other words, it evidently downloads trying to acccomodate how often you tell it to download.
I'm guessing about what you are describing.  Please clarify what is happening.

Gene