Module encode 

The encodings a message has to speak.

Base64, quoted-printable, RFC 2047 encoded-words, header folding, RFC 5322 dates, and SMTP dot-stuffing. None of it is interesting, and all of it is where mail actually breaks: a header that is one byte too long, a body line that starts with a dot, an accented name that arrives as mojibake.

Functions

base64_body

Base64 wrapped at 76 characters with CRLF, which is what a MIME body part must look like — an unwrapped 2 MB single line is not a legal message.

base64_decode

base64_encode

dot_stuff

Prefix any line that starts with . with a second one.

encode_word

Encode a header value as RFC 2047 encoded-words when it is not plain ASCII.

header_line

Write Name: value, folded so no line runs past [HEADER_WIDTH].

normalize_crlf

Every line ending becomes CRLF, which is the only line ending a message on the wire is allowed to have.

percent_encode

Percent-encode a filename for an RFC 2231 filename* parameter.

quoted_printable

Encode a body part as quoted-printable (RFC 2045).

rfc5322_date

Format a Date: header, RFC 5322 style, in UTC.

sanitize_header_text

Strip anything that would let a value break out of its header.

unique_token

A value unique within this process, for boundaries and message ids.