1. What is TNEF?
The proprietary format utilized by Microsoft Exchange server and Outlook e-mail clients is called "Transport Neutral Encapsulation Format". The Outlook client sends mail formatted Rich Text Format (RTF). The Exchange server believes it is always sending the message to a Microsoft email client, thus it formats and encodes it in a TNEF block. Message is then sent in two parts. One with text and formatting removed with the instructions in the TNEF block. When received by the Microsoft e-mail client , it processes the TNEF block. It is then re-formatted.
2. How does Domino handle it?
Problem is that Domino servers cannot decipher TNEF blocks. The TNEF appears as a sequence of hexadecimal digits in the message, however, in most cases it is composed as an attachment named "WINMAIL.DAT". In 7.02 and 8.0, this problem is remedied by new code (TNEF Converter) which scans the message for a TNEF object. The TNEF Converter is executed by the Domino SMTP task. Once a message is coming inbound via SMTP, the TNEF Converter will scan it for a TNEF object. If one is found, an extraction will take place creating new MIME part(s) then attaching the file attachment(s) to the message before depositing it in the Router's mail.box for delivery.
3. How to config to make it work?
TNEF Converter is enabled by ini parameter "TNEFENABLECONVERSION".
If TNEFENABLECONVERSION is enabled, the attachment named "WINMAIL.DAT" will be removed and the mail will be a plain text rendering of the rich text body and the original attachments (if the send uploaded in the sent mail).
Other related TNEF INI parameters:
- TNEFKeepAttachment: Keep the attachment "WINMAIL.DAT" in the mail
- TNEFAttachRTF: Create a Rich Text Blob containing original message in its original format as an attachment in the received mail.
Note that, TNEF Converter can not handle inline picture right now.