See METHODS in Mail::Reporter
Count the number of fields with this NAME. If the NAME cannot be found, the full header get loaded. In case we find any NAME field, it is decided we know all of them, and loading is not needed.
Get the data which is related to the field with the NAME. The case of the characters in NAME does not matter. When a NAME is used which is not known yet, realization will take place.
The body size is defined in the Content-Length
field. However, this
field may not be known. In that case, a guess is made based on the known
Lines
field. When also that field is not known yet, undef
is returned.