Information is MAIL360 Manager required in order for MailStream Plus to produce the USPS Shipping Services File (SSF)

MailStream Plus all versions
MAIL360 Manager all versions
MAIL360 Manager is a separate application from MailStream Plus (MSP).  It can be ran separately, or be called from within MSP.

MAIL360 Manager is required to generate serial numbers when the MSP IMBINB or IMBOUT parameter's position 44 is set to 'A' for automatic Serial Number generation. 
MAIL360 Manager is also required if the MSP IMBCTL parameter position 28 is set to X or M to generate the Mail Piece File.

But MAIL360 Manager is not required to generate the USPS Shipping Services File (SSF).  That file is generated by and within MailStream Plus.

For more information about the above mentioned parameters, please refer to the MailStream Plus Guide.
UPDATED:  February 15, 2018