We are having some random issues trying to open links from OWA. Links open fine from the full version of Outlook but from OWA we are getting 404 errors. We recently updated our cert but not sure if the timing is just a coincidence.

I don't think OWA does anything with links except show them on the page.  The link is acted on by the browser.

Hi,

Please switch to other browser to check this issue. (IE recommended)

Did you install any roll update in exchange 2010?

And please run UpdateOwa.PS1 to check this issue,

Open Exchange Management Shell as administrator:

1. Navigate to Bin Folder or Scripts for Exchange 2010 Server which contains UpdateOwa.PS1 script and run it as below!
2. .\UpdateOWA.PS1

Best Regards.

I'm having the same issue. No changes to cert since February. It seems to only effect long URLs. All work fine on outlook. Short URLs work fine in OWA, long URLs in OWA present in the error 404. Has anyone found a fix for this?

Figured it out. It's a problem with IIS request filtering. go into IIS Manager, double click on Request filtering, and 'edit feature settings.' I doubled both values. Url with more detail below...
http://www.iis.net/configreference/system.webserver/security/requestfiltering/requestlimits