Hi, the mailbox could be improved.

• I wanted to reply to a user with whom I already had a conversation, but their name didn't show up in the inbox.
  I had to guess the URL (https://www.watzatsong.com/en/conversation/USERNAME) to be able to reply to them.

• Moreover, I didn't see their reply either. I had to go to the aforementioned URL to see it.
  Their reply didn't appear at the top of the messages in the inbox.

• There should be a link to browse the older messages.

For information, I use Firefox 54.

Thank you for your work.