Since upgrading to version 91 of Thunderbird the performance of Thunderbird has been much slower. I have multiple email accounts and some of the folders are very large. I don't have measurements but the response time for simple things such as opening an inbox or syncing messages for an IMAP account is noticeably slower, taking at least two or three times as long as it used to (and for IMAP syncing, longer). Nothing else has changed on my system; internet connection is fine and fast, no windows updates lately. Are others experiencing this? I hope that a correction to this can be supplied soon. Thank you!