Can't access hughesnet email

[wgrobison1]

When I try to open hughesnet mailbox I get the message 

HTTP ERROR 504

Problem accessing ZCS upstream server. Reason: Cannot connect to the ZCS upstream server. Connection timeout.

everything else is working fine,  I notice the email icon shows Zimbra now, it lets me log in as usual but will hang on "loading" then the error message pops up

[wgrobison1]

the problem cleared itself after about 8 hours

[MarkJFine]

This seems to be a recurring issue at regular intervals that may coincide with security certificate reissuances - what's required to ensure the mail site can be securely accessed. It may be possible it fixed itself when the certificate for the upstream server was updated (ZCS = Zimbra Collaboration Suite, made by Synacor, HughesNet's email supplier).