Mail App keep crashing after install El Capitan

I'm so relieved. I found this thread very helpful. But I wanted to update with my own experience as I had the same crashing issue. Nothing worked that was said here accept one thing. I even made every email inactive and still crashing. Problem was the email I actually had just sent. So no matter what it would crash. Until I actually unplugged the Ethernet. Stayed open and I could go into my outgoing and delete it manually, then make the emails active again.

Whew. I was kinda not looking forward to maybe weeks of checking emails via my web sites and having to sift through spam etc .etc.

Thank you!!

I am using El Capitan 10.11.6 on a MacMini desktop that is cable connected to my ISP. I had Mail automatically open on startup (System Preferences>Users and Groups>Login Items). For some time now Mail has frozen after opening. I found that if I Quit Mail and restarted it I had no problem. My fix is to remove Mail from the automatic startup option and then open it manually.

Thank you so much for this helpful advise. My Mail app is now working again thanks to you.

Wonderful - Terrific - THANK YOU! It fixed my problem almost completely. At least I now can completely stop the bouncing back again and again without being able to stop it. I have found over the past couple of days that it has stopped flashing uncontrollably. It starts and waits so I can cancel it. Unfortunately I have another issue with my phone company that they are now having troubles. But I now stop the uncontrolled flashing altogether and can then look at each email address without any flashing! Thank You! Thank you! Thank you!

Removing the MailData folder did the trick for me. Thanks!

To BartoloTX - Thank you so much. That worked perfectly. Really appreciate it.