Encode or decode message bodies for 7bit transfer encoding. This is
only very little encoding. According to the specs:
RFC-2045 Section 2.7 defines legal 7bit data:
"7bit data" refers to data that is all represented as relatively
short lines with 998 octets or less between CRLF line separation
sequences [RFC-821]. No octets with decimal values greater than 127
are allowed and neither are NULs (octets with decimal value 0). CR
(decimal value 13) and LF (decimal value 10) octets only occur as
part of CRLF line separation sequences.
As you can safely conclude: decoding of these bodies is no work
See documentation in the base class.