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.