Migrating from W7 to W10. Thunderbird downloaded and installed. Mail files were on drive 2. After installation and the 3 profiles established, the file location was changed to the location on drive 2. Thunderbird was run to down the recent mail. The count in the Inbox increased as mail was downloaded. However, the new mail did not display. The file inbox.msf was deleted to get the mail reindexed. This did not resolve anything. The inbox file was removed from the mail folder. popstate.dat was deleted. Thunderbird restarted and the process of downloading 22,000 messages began. It would download about 250 (gmail) at a time. After about about 20,000 messages, the speed slowed to about 60-400 Kbps and 5 messages at a time. A posted suggestion was made to disable POP at gmail and then re-enable it. This brought the speed back to normal. The numbers were back to about 250. HOWEVER, the mail was being downloaded but not displaying in the inbox. About 14,000 messages were deleted and the inbox compacted. This did not improve the lack of displaying. It appears that the messages were not being displayed after the inbox was compacted and POP was disabled and re-enabled. Problem Resolution --- Given the above issues, rather than spend any more time, the following was done which has brought about an acceptable resolution without understanding what or why: 1. The files: inbox, inbox.msf, popstate.dat were deleted. The old inbox file had been moved to another folder earlier. 2, The email user configuration was changed from user@gmail.com to recent:user@gmail.com. This caused the last 30 days of email to be downloaded, 2,100 messages. The download speed was typically 1.2 - 2.5 Mbps. However, it did spike to 71 Mbps. Observation: The green progress indicator did not function properly. The window was either completely green or only the background color. On the left side, the progress nnn of 2100 messages was correct. The green color came and went a few times. If I need to refer back to the old messages, the old file can be brought back into the mail system as a folder or a non communicating account as a 4th profile. At this point, I am not aware of any irregularities in the operation of Thunderbird 52.60, with Windows 10. This started out as a question seeking help. However, as it was being written, my thinking changed to a solution that would allow me to proceed. However, I wanted to point out that there are some issues with Thunderbird downloading mail and not displaying it in the inbox.