"No user found for session"
 

When I try to view an attachment (by checking the box near the attachment and clicking "View") I get a web page blank except for the message "No user found for session."

I AM able to download an attachment by clicking the Download button, but I'm wondering why I can't view an attachment and what the "no user found for session" means.

I am not experiencing this issue using Google Chrome in Windows 10.

Is this a consistent issue that seems to happen always whenever you try to view an attachment, or is it something that happens only sporadically? Does a new tab open when you click on View? Is that tab still within FastMail? Have you tried this with a simple text attachment? Have you tried opening the browser in safe mode?

If the above does not point at the cause of the issue, then it may be browser/operating system specific.

On the face of it, it would suggest that FastMail on the server is seeing a session id from the client which does not match any that it knows about. That is typically a communication issue between the client and server, a bug. However, it is always important to remember that error messages can be bogus (a message produced whenever some kind of generic issue appears in that part of the code, and representing the developer's assumption as to the most likely cause) with the real error something different.

Thanks, BritTim, I think you have hit the proverbial nail on the head! I use FastMail with an SSB (Single Site Browser) based on Chrome (so that FM appears to be its own app which I can easily find in the Dock so that I don't have to rummage through too many open windows to find it). The SSB (named "FastMail") is set so that when I click on a link in an email in the SSB, the link opens in (regular) Chrome. Of course, this means that the link is passed to a different app (or, at least, a different instance of Chrome). Presumably this is what is upsetting FM's server.

I vaguely remember when I was setting up the SSB I read in the docs that it can be set up to open certain links (from certain domains) in a second window of the SSB rather than in (regular) Chrome, and I remember thinking "Why would I want to do that?" I guess now I know!

Thanks again...I'll check out this idea later today.