I'd already played with all the white-space, word-wrap, width, overflow, etc settings I could think of any the only one that seems to effect it is word-wrap: break-word, as I mentioned earlier. With that set, the text wraps as it should, but obviously not as desired since it breaks in the middle of words. With any other setting, the line doesn't break at all. It's almost like it doesn't treat the white-space as a line-breakable entity.

The width does indeed show as the width of the page and reducing it does show (at least according to firebug outline) that the block is shrinking. However, the text goes beyond the right side of the p block.

Huh... more fun :) Clicked firebug's 'edit' on the p block and it comes out with this:

<p>This&nbsp;is&nbsp;a&nbsp;really&nbsp;long&nbsp;line&nbsp;that's&nbsp;a&nbsp;really&nbsp;long&nbsp;line&nbsp;a&nbsp;reallaiwefoi&nbsp;aweoif&nbsp;owaiefoai&nbsp;fawe&nbsp;ofiwae&nbsp;ofiawo&nbsp;igeoawigo&nbsp;awefoiwaoef&nbsp;aowig&nbsp;oawie&nbsp;goiawogi&nbsp;awoige&nbsp;owa&nbsp;goiwa&nbsp;goia&nbsp;wogi&nbsp;aowig&nbsp;oawi&nbsp;goiaw&nbsp;ogi&nbsp;waoei&nbsp;owaeif&nbsp;owaig&nbsp;owaie&nbsp;o<span rtenodeid="1" id="ms-rterangecursor-start"></span><span id="ms-rterangecursor-end"></span><br></p>

As evidenced by the reply above, non-breaking spaces, are non-breaking ;)

Somehow OWA is replacing all spaces with non-breaking ones. Not sure how to best handle that...

Oddly enough, the same actions in chrome, result in a p block as follows:

<p>aoief oaiwjef oiajwe ofijawoe ifjoawi ejfiajw eofij;a woeijf ;awoiejf ;oaiwje ;foia jw;eofij a;woei jf;oaiw jef;oia jwe;of ija;woei fj;aowi ejf;oi jwaeofij awoei jfoiwa jefoiwae jofiaj woeifj owaie jf<span id="ms-rterangecursor-start" rtenodeid="1"></span><span id="ms-rterangecursor-end"></span><br></p>

With no &nbsp replacement, so it works just fine.

The non-breaking spaces are the most logical culprit. But why are they there?

Rich text editors using a lot of scripting, and it may be that Firefox's numeric code or virtual key code for a spacebar press is somehow lining up with what the script expects for a non-breaking space.

Very puzzling and hard to work around without serious hacking (e.g., a userscript customized for the site).

Microsoft has posted an incident on the Office365 Dashboard.

Current Status: Engineers have identified an issue in which some customers are experiencing degraded functionality when accessing the Outlook Web App (OWA) with Firefox. When the Outlook Web App (OWA) is accessed with Firefox, the word-wrap feature does not function as expected when composing a message. This issue does not occur when using other internet browsers. Investigation determined that a coding issue caused compatibility issues with the Firefox browser. Engineers have developed a fix and are deploying it across the affected environment to mitigate end-user impact. As the fix is deployed across the affected environment the some customers will see feature restoration.

Customer Impact: When accessing the Outlook Web App (OWA) with Firefox as the internet browser, word-wrap formatting does not function properly when composing a message.

Workaround: As a workaround, customers can access the Outlook Web App with Internet Explorer. (NOT AN OPTION FOR ME AT THIS TIME)

Incident Start Time: Tuesday, April 15, 2014, 8:00 PM UTC

Estimated Time to Resolution: The deployment process is expected to complete by Saturday, May 3rd, 2014 at 8:00 PM UTC.

Preliminary Root Cause: Investigation determined that a coding issue caused compatibility issues with the Firefox internet browsers

Thanks so much for this update/information...

Microsoft posted that the Office365 restore is done. I tested OWA in Firefox and the word-wrap worked great for me. Thank you for all your help.