Freron MailMate

Hello!

Since today MailMate (on Mac OS X 10.14.3) does not start any more... I need my mails urgently for business!
When I start it, no window ever appears and I have to force quit it again.

When I start it at command line (/Applications/MailMate.app/Contents/MacOS/MailMate):

2019-04-23 09:56:37.112 MailMate[1217:21224] NSExceptionHandler has recorded the following exception:
NSUncaughtSystemExceptionException -- Uncaught system exception: signal 10
Stack trace:  0x7fff3efbdcbb  0x7fff6a0d7b3d
2019-04-23 09:56:37.115 MailMate[1217:21224] NSExceptionHandler has recorded the following exception:
NSUncaughtSystemExceptionException -- Uncaught system exception: signal 10
Stack trace:  0x7fff3cdc9221  0x7fff68e20c81  0x7fff67620dfe  0x7fff67620be2  0x7fff67613bb9  0x7fff68e1e85a  0x7fff3cd6b87d  0x7fff3efbdcbb  0x7fff6a0d7b3d
Assertion failed: (NSViewIsCurrentlyBuildingLayerTreeForDisplay() != currentlyBuildingLayerTree), function NSViewSetCurrentlyBuildingLayerTreeForDisplay, file /BuildRoot/Library/Caches/com.apple.xbs/Sources/AppKit/AppKit-1671.20.108/AppKit.subproj/NSView.m, line 14143.
2019-04-23 09:56:38.143 MailMate[1217:21224] NSExceptionHandler has recorded the following exception:
NSUncaughtSystemExceptionException -- Uncaught system exception: signal 4
Stack trace:  0x7fff3efbdcbb  0x7fff6a0d7b3d  0x1101fb000  0x7fff69f951d8  0x7fff69f5d868  0x7fff3a2f511c  0x7fff3a2f4f4f  0x7fff3a2f4eb5  0x7fff3a2f4d27  0x7fff3a2efe2a  0x7fff3a2ef99f  0x7fff47c5025b  0x7fff47c4fc22  0x7fff47c7b5ed  0x7fff6a0e06c2  0x7fff6a0e3679  0x7fff6a0e0473  0x7fff3eff64ca  0x7fff3efbdc7f  0x7fff3cdc9221  0x7fff68e20c81  0x7fff67620dfe  0x7fff67620be2  0x7fff67613bb9  0x7fff68e1e85a  0x7fff3cd6b87d  0x7fff3efbdcbb  0x7fff6a0d7b3d
libc++abi.dylib: terminate_handler unexpectedly threw an exception
2019-04-23 09:56:38.165 MailMate[1217:21224] NSExceptionHandler has recorded the following exception:
NSUncaughtSystemExceptionException -- Uncaught system exception: signal 4
Stack trace:  0x7fff3efbdcbb  0x7fff6a0d7b3d  0x7fff00020008  0x7fff69f951d8  0x7fff67615231  0x7fff67620e24  0x7fff67620be2  0x7fff67613bb9  0x7fff68e1e85a  0x7fff3cd6b87d  0x7fff3efbdcbb  0x7fff6a0d7b3d
2019-04-23 09:56:38.169 MailMate[1217:21224] NSExceptionHandler has recorded the following exception:
NSUncaughtSystemExceptionException -- Uncaught system exception: signal 4
Stack trace:  0x7fff3cdc9221  0x7fff68e20c81  0x7fff67620dfe  0x7fff67620e73  0x7fff67620be2  0x7fff67613bb9  0x7fff68e1e85a  0x7fff3cd6b87d  0x7fff3efbdcbb  0x7fff6a0d7b3d
Killed: 9

Please tell me how to get rid of that, it's not 10:07 AM here and I wasted already 1 hour at least :-(

Kind regards,
Christian