Why does decoding the following fail
Subject: =?ISO-8859-1?Q?Begr=FC=DFungsschreibe?=n
while decoding the following works?
Subject: =?ISO-8859-1?Q?Begr=FC=DFungsschreiben?=
I read https://www.rfc-editor.org/rfc/rfc2047 but could not find a note that there must be space after the end mark ?=. That's the only difference between the two lines. In the first line (which is the failed one) there is the n directly after the end mark.
I used Python 2.7 for decoding.
I googled for a bug in Python, but could only found resolved issues.
an 'encoded-word' that appears in a header field defined as '*text' MUST be separated from any adjacent 'encoded-word' or 'text' by 'linear-white-space'.
The Subject header is defined as *text (and in any case the errata add the same restriction more generally to section 2).