VERIFIED SOLUTION i

MailStream Plus - Does 8.3.3 support the RMR file (REFERENCEABLE MAIL RECORD) that's new in Mail.dat 17-1?

MailStream Plus 8.3.3- all platforms
 
No, version 8.3.3 does not support the RMR file.  Per the current tentative schedule, the RMR file is planned to be supported in the MailStream Plus 8.3.4 release.
UPDATED:  March 23, 2017