I've had this problem for a long time. On my main computer, Thunderbird is usually very slow connecting to the Comcast email server. It typically takes about 40 seconds to connect to start downloading messages and about 30 seconds to connect to upload. Sometimes it connects without the long wait. I have a backup computer with Thunderbird, and it connects right away. The computer that works well uses Windows Defender. The slow one (my main computer) uses BitDefender, but I used to use Kaspersky. Both use 64-bit Windows 10 home. What can be causing this slowdown, or how can it be fixed?