Content Transfer Encoding
Content Transfer Encoding Base64 Decode
The base64 is a totally mapped and fairly efficient encoding scheme for binary files. The quoted-printable scheme is used for mostly 7-bit data and is readable by humans. There are three values of content-transfer-encoding that can be used in Internet SMTP messages. The 7bit is the definitive SMTP mechanism.
[This was originally posted in Outlook IT Pro but ran into a dead-end there.] I'm running Outlook 2010 with a hosted Exchange 2007 server. If I reply to a plain-text message encoded in UTF-8, the recipient receives the reply in content-transfer-encoding=base64. How do I disable that (ie, either leave the message in utf-8 or quoted-printable)? KB#278134 describes the problem but states 'When Outlook uses Exchange to send the message, Outlook does not honor this registry setting.' When I reply using OWA light to messages with the following MIME header Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit 8bit the recipients (gmail & pop) get Content-Type: text/plain; charset='Windows-1252' Content-Transfer-Encoding: quoted-printable This is ok. When I use Outlook through Exchange 2007, the recipients get Content-Type: text/plain; charset='utf-8' Content-Transfer-Encoding: base64 This is bad.