"Internet Message Formats" does not affect the communication among MAPI mail clients within the same EXCHANGE ORGANIZATION.
When SMTP virtual server sends a MAPI message to an Internet client, it assigns a content type (MIME) to attachments based on the extension of the attachment file.
Right client the "Internet Message Formats", you can modify the MIME types used in your ORGANIZATION.
Control the "Message Formats" for Internet SMTP domain
We have three Internet SMTP Organizations: Study.COM, Delta.Com, and Contoso.com.
Study.COM and Delta.COM use EXCHANGE SERVER 2003, whereas Contoso.com uses Unix Sendmail.
All the three Organizations are partners. All of them support Message Format of HTML and Plain text.
However, Contoso.com (Unix) will never use the Rich Exchange Format.
Only the communication among three Organizations is required to have the following features:
Allow Out of Office Response
Allow Automatic Reply
Allow Automatic Forward
We create two SMTP domains: Contoso.com and Delta.com and modify the Advanced Message Format accordingly.
The default(*) SMTP domain matches all other domains.
