When creating an HTML Email Status report I notice that I'm not getting the records for emails that were sent in Mass Email (e.g. Mass Email Contacts) Who can I report on Email Status for such mails?
You need to configure the appropriate filters to match your mass email and then run the 'HTML Email Status' report. Apply filters to categorize your mass emails hierarchically using multiple criteria - e.g. by date first, and then email template name. Filters should be applied so that they only match your mass email campaign and NOT other emails.
For e.g. If you'd like to know the status of mass emails sent out on Christmas day, you would run the report then filter by that date (25th December 2013) and then by email template name used in the mass mail campaign. The important thing here to note is that the report does not know those filters our specific to mass email.
I had faced the same issue some time back and this thread with the above mentioned approached helped me.