Hello,

Email correspondence type is for outgoing email messages, where the body of the message is stored in an instance of the Data-Corr-Email class and the addresses are stored as instances of the Data-Address-Email class. Outgoing email that is formatted for display on a modern email client program (such as Microsoft Outlook) may contain HTML markup and email attachments copied from work item attachments. Other outgoing email may contain only text.

Fax correspondence type is for outgoing letters to be sent by fax transmission through the Correspondence Output Server

Thanks,
Gisela