I am running OUtlook for MAC and for the past couple of weeks I get a message now and then that says unable to send mail.

When I open this window it lists several e mails and says the date & Time, then "message could not be sent"

It references an error code 50.

This does not happen on all my outgoing mail, only some.

I cannot open the mail from this box to see what messages it is referring to.

Any one ever seen this?