Outgoing email "Internal Server Error" SuiteCRM 7.4 Beta 2

Hello, I have just installed a brand new SuiteCRM 7.4 Beta 2 for test. When I set up the incoming and outgoing mail configure well, I can receive the email well. But when I try to send out an email, there is a Exception occured, the system shows a popups “Internal Server Error”.

I am not sure if this is a bug, but I am sure my setting is all correct, because it works well in SuiteCRM 7.3.1.

Have you set up your email Settings in Admin -> Email Settings?

Hi Will, I am sure all setting is correct! Because I have two CRM system using same setting, the other system is using 7.3.1, and I can send the email well.

Hi Will, I‘ve tested this problem again!
When I set up all email configure in 7.3.1, I sent an email successfully. Then I upgrade the system to 7.4 Beta2, the problem occured.
Hope this problem could be solved in the SuiteCRM 7.4 version on 19th Oct.