Hey Vince, sorry to hear you're having these issues! The first thing I'd recommend checking out is seeing if the user's issues persist in a guest or incognito session in the browser (or another browser) as that will eliminate any browser addons, caches/history, settings, etc as a possible culprit. 

The other thing I'd recommend having this user check out is the KB article below. This pertains specifically to logouts and whatnot but the causes described here can have a number of odd effects on webmail if not set up correctly:

Hi Kyle,  Yes, they were using chrome and I suggested to try  Edge.  The issues exists in both.  This is the only account in that domain that is having a problem.  Webmail is used exclusively.  

Okay in that case then - are you able to replicate as well if you impersonate their account? If so, there is definitely something in the account causing problems and I'd be on the lookout for large JSON files in their account, large images in their signature, etc. If you submit a ticket on this I'd be happy to help dig into it!

+1 to what Kyle said.  We've had users upload very high-resolution images (exceeding 4000 x 4000) in their signature and it dragged webmail to a crawl.  Even though the image itself was only around 10 MB which is NOTHING on high speed connections, it was enough to drag webmail itself down to pretty much not usable.

I don't know exactly why, or what happens in the background to make a mere 10 MB so impossible to process, but as soon as those images were removed and replaced by an appropriately sized (200 x 200 range) image, performance was vastly improved for the affected users.

 

Hi Guys,

OK, I will look at those items.

Thanks