see discussion in #97 and #98 (the break just breaks out of the inner loop, the messages still get iterated over)

for example this player-entry here:

local entry = {
 inbox = {
  { id = "a" },
  { id = "b" },
  { id = "c" }
 }
}

and if you want to delete messages with the following msg_id's:

msg_ids = { "c", "b" }

The mail with id c will get matched first and removed, after that the inbox looks like this:

inbox = {
  { id = "a" },
  { id = "b" }
}

But the inner loop still continues with the exact same i value and tries to dereference inbox[3] (which it does not find)

The break ensures that the i iterator value is actually sane and does point to a valid entry.