Mail disappeared?

Hello everyone. About 20-25 days ago I mailed some stuff to a second character of mine because I had no space to keep it, mostly mining supplies which I wanted to use later to level up a profession. When I checked in today, I found a lot of mails missing. And weirdly enough there are a lot of empty mails from an unknown sender. (https://imgur.com/TLYiC4E)

Anybody have an idea? I lost a lot of stuff...

After around 3 hours the mail showed up again. Weird stuff, but at least I have all my mats :)