From: test@example.invalid
To: test@example.invalid
Date: Sun, 19 Jul 2020 17:03:56 +1000
Subject:
 =?US-ASCII?q?Hans Martin Djupvik?= =?ISO-8859-1?q?,_Ingrid_B=F8?=
 =?KOI8-R?b?LCDp0snOwSDzycTP0s/XwQ?=
 =?UTF-16?b?//4sACAASgBlAHMAcABlAHIAIABCAGUAcgBnAA?=
 =?UTF-7?b?LCBGcmlkYSBFbmcrQVBnLQ?=
 bad: =?UTF16?q?badcharsetname?= =?US-ASCII?b?/w?=
 =?UTF-7?Q?=41=6D=65=72=69=63=61=E2=80=99=73?=

The subject header contains various RFC2047 encoded words.
For completeness we test both base64 and quoted-printable, and some
ASCII-incompatible encodings.
We also include some bogus words which cannot be decoded.