Hello!
The format of encoding is described in RFC 2047 - "MIME Part Three: Message Header Extensions for Non-ASCII Text".
According to the standard, encoded string has the form: =?<charset>?<encoding>?<encoded-text>?=
- The 'charset' portion specifies the character set associated with the unencoded text, for example UTF-8.
- Initially, the legal values for "encoding" are "Q" and "B". The "B" encoding is identical to the "BASE64" encoding defined by RFC 2045.
To decode "encoded-word" with Procmail you will need to use a external program. The widely used Linux utility for encoding/decoding Base64 is base64 from GNU coreutils.
But there are important moment: how you will use decoded text in Procmail? We need discuss it in private chat.
I will be glad answer on any questions!
Thank you for attention!