Mac Mail Inbox Turned Into A Bunch Of "MailL Attachment.eml" Icons

[PGB1]

Hello All!
I hope this note finds everyone well & enjoying today!

On my MacBook Pro (2007 Using OS X 10.11.6), I have several e-mail addresses, from 3 different mail servers, in Mac Mail. All but one of them are behaving.
Today, instead of the usual list of messages, one of them presents me with several icons that are titled "Mail Attachment.eml". (Screen shot below)
If I doble-click any of them, they are mail messages (not necessarily attachments, such as photos or files).

I searched all the drop-down menu bar items and all over Mail - Preferences and don't see a solution.

Do any of you know what went wonky & how to get the normal list of messages view back?

Thanks For Helping!
Paul

View attachment Inbox Odd View.pdf

 

[ferrarr]

Have you restarted your MBP?

 

[PGB1]

Thanks Bob for taking time to reply.
Sorry for the delayed reply on my part. I haven't gotten the usual e-mail notifications when a reply is posted.
I've restarted a bunch of times since this showed up.

It sure is curious to me.
I suppose if I have to, I can try to forward the messages to myself and see what happens.

Actually Mail is getting quite goofy lately in other respects, too. But I'll post those questions separately if I can't figure them out.