Event EVENT_MAIL_CLOSE_MAILBOX fired upon closing of inventory?

[Baertram]

I just debugged some sourcecode and found out that the following event "EVENT_MAIL_CLOSE_MAILBOX" will be fired if the inventory of the player gets closed?
It fires even 3 times if I open the mailbox and close the mailbox afterwards sometime?

EVENT_MANAGER:RegisterForEvent(gAddonName, EVENT_MAIL_OPEN_MAILBOX, Open_Mail_Panel)
    EVENT_MANAGER:RegisterForEvent(gAddonName, EVENT_MAIL_CLOSE_MAILBOX, Close_Mail_Panel)
 
--Event upon opening of the mail panel
local function Open_Mail_Panel()
    d("Open_Mail")
end
 
--Event upon closing of the mail panel
local function Close_Mail_Panel()
    d("Close_Mail")
end

Is this normal and wished?
Or do I have to unregister the event in the "Open_Mail_Panel()" function and register it again in "Close_Mail_panel()" function?

Thanks