EmC slow download of mail or not at all

I have the most recent version of EmC free on a Windows 7 computer. I’m finding the program almost impossible to use due to the long download times for some messages from Yahoo and complete failure of others. When the mail fails to download I am left looking at a blank panel with 5 dots travelling left to right at the top of the screen - but no download. SOME emails are OK and some eventually appear after maybe a minute. I have the download messages for offline use box checked in accounts. Thanks for any help received.

Do you use any antivirus software? If so, does it help if you disable it?

Just Microsoft Essentials - I don’t know how to disable it I’m afraid. Thanks.