Giant font sizes in mails sent from Monterey Macs.

Here's a screenshot of an email with font problem.

UPDATE & Workaround:

I could reproduce this problem with an 2016 Intel MacBook Pro with Monterey installed. Every email I sent with Outlook had some giant lines, but when I used Apple Mail, there were no problems.

Then I noticed "Revert to Legacy Outlook" menu under "Help" and I reverted to the older Outlook interface. And the problem is gone. I compared the mail sources of these messages, older Outlook puts very much less Word tags at the top of the email. It's just fine.

I'm not sure this was a Monterey only problem.

I asked the hosting company to check for any message body alterations by an antivirus filter etc. They analyzed affected messages to no avail. There's no addin to alter the content of the mails. They're on Postfix server with Zimbra webmail application.

My Google search find a similar problem, someone claimed COM addin for Outlook for Windows removes the dot in 11.0pt so it becomes 110pt. But this would appear in client side only, this change appears in IMAP server.

There might be a problem with Monterey's BASE64 encoder, so they are decoded incorrectly.

No, it's 10pt in sent mail.

Giant text may also occur in email signature and in quoted text. And only one paragraph is affected.

We tried different fonts and sizes. Plain text is not a solution. As this is a graphics business there are lots of inline images, colored revised texts etc.

We'll try an older Office version.