I posted this question on the Mozilla Thunderbird forum but thought I'd also post it here since it involves Windows 8 and 8.1. It is an interesting problem that does show a small amount of occurrence if searched out online. However I've never found a fix for it and the solution I finally came up with on my own hasn't been mentioned anywhere I've found over the past 6 months.

I have 2 desktops running Windows 8 and a Dell laptop running Windows 8.1. I'm running Thunderbird 31.6 on all three.

Originally all 3 were running Windows 8 but I figured I'd give Windows 8.1 a try on the laptop. I did this upgrade about 6 months ago.

Before doing the upgrade on the laptop Thunderbird was running perfectly. As soon as I did the Windows 8.1 upgrade I ran into a problem getting Thunderbird messages to download as soon as I opened the program. I have 4 email addresses on the laptop with a medium amount of stored messages in folders set to automatically compress. The two desktop computers have far more messages stored in their folders and there is no problem getting mail to download immediately at startup. No messages are left on the servers on any of the 3 systems.

To get mail to download the quickest possible way on the laptop I had to set one email address (earthlink.net) to SERVER SETTING, CHECK FOR MAIL AT STARTUP and the other 3 addresses NOT to check for mail at startup. Then the earthlink address would only take 3 or 4 seconds to do the check and download messages. Once that was done I could click on GET MESSAGES, GET ALL NEW MESSAGES on the drop down menu and all addresses would download immediately. If I had the server setting for all 4 addresses set to CHECK FOR NEW MESSAGES AT STARTUP then it could take 15 to 20 seconds for mail to download and Thunderbird would be locked up for that period of time. If I had no addresses set to check for messages at startup then the program would start as it should but as soon as I clicked on CHECK FOR ALL NEW MESSAGES in the drop down window the program would freeze for that 15 to 20 seconds.

Over the past 6 months I tried many things to solve the problem that did not work. The problem persisted no matter what version of Thunderbird was installed. I tried standard and beta versions all the way back to around 22.0 and up to the current beta and standard versions.

The other day I was again searching for a solution to this problem and stumbled upon a site that talked about TOOLS, OPTIONS, ADVANCED and then DISK SPACE and COMPACTING settings. After working with this for a few minutes and getting nowhere I tried for the first time changing the PROXY settings in the same window.

VOILA !!!! Problem finally solved. As soon as Thunderbird starts all 4 email addresses are immediately checked and messages downloaded just as on the 2 desktop PCs. There is no freezing of Thunderbird either....it's just simply working correctly.

The change I made was in CONFIGURE HOW THUNDERBIRD CONNECTS TO THE INTERNET, SETTINGS. I unchecked USE SYSTEM PROXY SETTINGS and checked NO PROXY. This change fixed the problem. I also tried checking AUTOPROTECT PROXY SETTING FOR THIS NETWORK and that reinstated the problem. As such I now have NO PROXY checked in that window.

While this is what I had to do on the laptop to get Thunderbird to immediately check for and download message on all 4 addresses the two desktop PCs remain set on USE SYSTEM PROXY SETTINGS and are working as they should. The only difference in overall setup that I can see is that Windows 8 is on the desktops and Windows 8.1 is on the laptop.

However........I don't understand proxy settings and how they affect system security etc. Can someone explain this and let me know if leaving this set at NO PROXY could cause me problems down the road?