First things first: You're using version 2.1.9 of JForum, which is obsolete and has numerous security holes for which exploits have been publicly posted.
You should upgrade ASAP to the latest version 2.4.1, which is available at
https://sourceforge.net/projects/jforum2/
As to your question, I don't understand what you mean by "mail page" - there is no such page in JForum. Do you mean the private message pages? The screenshot you posted is the forum home page - what's strange is that it shows no forums, even though the bottom info says that a topic has been posted. Does the user who is logged in have access to that forum?