Decode the utf8 to ISO-8859-1 mail subject to text in .procmailrc file

Question

Set out to write a simple procmail recipie that would forward the mail if it found the text "ABC Store: New Order" in the subject.

 :0
    * ^(To|From).*[email protected]
    * ^Subject:.*ABC Store: New Order*
    {

Unfortunately the subject field in the mail message coming from the mail server was in MIME encoded-word syntax.

Subject: =?UTF-8?B?QUJDIFN0b3JlOiBOZXcgT3JkZXI=?=

The above subject is utf-8 ISO-8859-1 charset, So was wondering if there are any mechanisms/scripts/utilities to parse this and convert to string format so that I could apply my procmail filter.

Answer 1

You may use perl one liner to decode Subject: before assigment to procmail variable.

# Store "may be encoded" Subject: into $SUBJECT after conversion to ISO-8859-1
:0 h
* ^Subject:.*=\?
SUBJECT=| formail -cXSubject: | perl -MEncode=from_to -pe 'from_to $_, "MIME-Header", "iso-8859-1"'

# Store all remaining cases of Subject: into $SUBJECT
:0 hE
SUBJECT=| formail -cXSubject:

# trigger recipe based also on $SUBJECT content
:0
* ^(To|From).*[email protected]
* SUBJECT ?? ^Subject:.*ABC Store: New Order
{
....
}

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Comment (2020-03-07): It may be better to convert to UTF-8 charset instead of ISO-8859-*.