Installed Thunderbird on my mother-in-law's PC and set up IMAP so that she can work offline with her email. This is an existing yahoo account that has various folders. It works fine (sends and receives messages) except that startup takes ages 5-10 minutes making it basically unusable. Problem persists when all add-ins are removed (including lightning), when starting in safe mode, and when starting offline. Other applications (e.g. Excel, Word, Firefox) start up quickly and normally. The problem is not due to slow internet connection. Please let me know if there are any obvious causes of the problem or solutions. Thanks. Tim Thunderbird version is 38.5.1 Antivirus software is Avast 11.1.2245 System info: OS: Windows 7 Home Premium Version 6.1.7601 Service Pack 1 Build 7601 System Model HP G62 Notebook PC Processor Intel(R) Core(TM) i3 CPU M 350 @ 2.27GHz, 2266 Mhz, 2 Core(s), 4 Logical Processor(s) BIOS Version/Date Hewlett-Packard F.48, 2011-11-09 Installed Physical Memory (RAM) 4,00 GB Total Physical Memory 3,80 GB Available Physical Memory 2,22 GB Total Virtual Memory 7,60 GB Available Virtual Memory 5,05 GB