Message stuck in Queue folder

The reason it is stuck I do not understand. If I send it, I receive a
message that the domain is unknown. The error is my fault of failing to
have a period in the domain part of the address. 
(destinationorg, not destination.org) And the message is still in the
Queue folder, Claws-Mail tries to send it again, and I get the same
error message. 

I am unable to delete the message after many tries; I cannot edit it to
insert the needed  period, or otherwise modify the message, so now
wonder if there is any way to clear it from the folder.

I know I'm using an old version of Claws. If I updated the version to
4.0.0 or better, would the message go away?

Suggestions are welcome.

Henry C.