There is some Microsoft Office-specific coding there, for example: MsoNormal, MsoHyperlink. I'd usually expect to see that when replying to or forwarding a message which has passed through Outlook.

Did you write this message from scratch, or is it a reply to or forward of something created elsewhere?

Or are you using a signature created in Word or similar?

Hi Zenos,

I did reply to a previous email in Thunderbird in order to quickly pickup a bunch of addresses so I wouldn't have to reenter them manually. I deleted the previous body (CTL-A to select, I believe, but it could have been selecting most of the lines by mouse, then DEL), and then typed my new message. I also retyped the subject line. At the time I tried to send, the only text visible was what I had entered, the updated subject line and the email addresses. Whatever Spell Checker was reacting to, it was not visible to the user.

This kind of action has worked fine in the past. This is the first time I've seen any kind of unwarranted behavior similar to this by Spell Checker.

I do not have a Signature.

-Steve

It's a known problem with the spell checker, but as I said, usually associated with the verbose markup put into email messages by Outlook. Any email created by Outlook effectively has a document template included. Try ctrl+u to see the raw message.

A recent discussion about this very topic: https://support.mozilla.org/en-US/questions/1112823#answer-853791 led to a finding that Thunderbird has a look-up table of html tags it anticipates finding in emails, but some commonly encountered tags (e.g. <div>) are not in this table and so get spell checked rather than skipped over. Clearly, the mso stuff isn't in Thunderbird's table either.