Often when I right click the mailbox to open it, it does nothing.
Relogging fixes it, but the thing is, this is often right after logging in! And, opening the mailbox is normally the first thing I do every time I log in, so I don’t know what else this bug may affect.
have you ruled out addons causing the problem?
It happens on some logins, not others, with no addon change. There’s no lua error when I do an unresponsive click. How would it be an addon?
That said, I don’t see how I even could check, since it seems to be random whether or not it’ll happen on login.
Go into your WoW install folder and delete the WoW Cache contents. There is likely something corrupted in there that is causing this. That said, addons can break for some alts but not others, work sometimes, then bug out later. It’s always a good idea to back up and reinstall addons occasionally.
I also experienced this issue; however in my character’s case, it was related to a particular mailbox (other mailboxes worked as expected). The mailbox in question was the one at 52.8, 75.8 in Orgrimmar (outside the Valley of Strength Auction House), and it did work properly for other characters in play at the time (asked another player to confirm it was working for them).
After logging out and back in, the mailbox returned to proper functionality for my character (Kild of Wyrmrest Accord) as well. This is not the first time I have encountered this issue, and it seems to be unrelated to any addons or client-side influences.
This mailbox just temporarily behaved as a non-interactive instead of functional item, and /reload does nothing to change this behavior. I did not test if leaving and re-entering the zone would remedy this problem since it was resolved after logging out and back in.
*edited to add paragraph spacing for readability