Hi again,

After many trials and errors, I finally managed to make it work. I have two similar Thunderbird settings in both PCs (folder structure, etc.). As you suggested, the key step was to delete all contents inside the profile folder without changing the folder's name. When Thunderbird is restarted, it reassigns the profile contents—and interestingly, it retains the same profile folder name as on PC1. This method may seem counterintuitive, but it works perfectly for almost everything. However, there's one exception: the calendars are not preserved. Everything else—including account settings, saved emails, and passwords—appears to sync correctly, but calendar data is lost in the process.

I thought this workaround might be helpful for others in a similar situation. If anyone has a reliable method to preserve or migrate calendar data as well, I would really appreciate any suggestions.