In 3.11 on a 64 bit Linux platform crashes every time. I have 8 IMAP accounts and one folder (MH) where I move some of the messages through filter rules. Claws mail crashes when clicking on a folder with unread messages. It takes a lot of time do do whatever it does and ends up crashing almost every time. The message on the bottom bar is "Setting summary from message data" and the cursor keeps rotating until the whole thing crashes. It mostly crashes on folders from the MH created repository and on sub-folders folders in a IMAP structure such as the GMAIL labelled folders. Please do not close the bug before checking all these options. On simple INBOX folders seems to be fine. Most likely the problem is with sub-folders and special MH folders For me is unusable at this stage. It used to work fine before upgrading to 3.11
This is similar to #2899
Like bug #2899, it works for me. Nothing changed in relation to this in 3.11.x, so it's likely the problem resides somewhere else on your system and this is the side effect. You'll need to provide more information, please see http://www.claws-mail.org/faq/index.php/Debugging_Claws and re-open this bug report when you have more info.
I found the problem. The culprit is the gData plugin I disabled the plugins one by one until I found what crashes claws. Check/enable the gData plugin and probably you will be able to reproduce the problem. Can you somehow protect the program from bad plugins?
Likely the same cause as #3386. If it still crashes for you, please re-open with a backtrace.