Player mail is limited to 12 items. Blizzard mail can be 16 items long. I ran into this issue when leaving items on corpses in wow remix and the last 4 items in the mailbox crates were being missed for each mail.

This can be fixed from changing ATTACHMENTS_MAX_SEND to ATTACHMENTS_MAX_RECEIVE in the main lua file. I'll be creating a pull request with the solution in a bit.

This needs to be tested before being fully merged in as I don't know how to properly test the addon. It currently throws no errors for me using bugsack when opening the mailbox.

pull request: #17