VERIFIED SOLUTION i

Does new USPS PostalOne Mail.dat Clients affect MailStream Plus

Sometimes the USPS releases new Mail.dat Clients, and sends out notifications like this-
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Please note the change in deployment for PostalOne! Test Environment for Mailers:
PostalOne! Oracle 12C Upgrade to Test Environment for Mailers (TEM) - will occur on Monday, August 21, 2017 between 6:00 AM to 6:00 PM CT. The PostalOne! TEM environment will not be available during this time. 
PostalOne! Releases 45.3.1.0 Deployment to Test Environment for Mailers (TEM) - will occur on Monday, August 21, 2017 between 6:00 AM to 6:00 PM CT.  The PostalOne! TEM environment will not be available during this time. 

PostalOne! Release 45.3.1.0 – PostalOne! Release 45.3.1.0 will deploy on Sunday, August 20, 2017 , between 12:00 AM to 8:00 PM CT.  The PostalOne! system will not be available during this extended window.  

•    A new Mail.dat® client download 45.3.1.0 PROD will be required after this release.  All previous versions of the Mail.dat client will be expired.
•    The PostalOne! system and Mail.dat® will be disabling Secure Socket Layer version 3 (SSLv3) and only allow Transport Layer Security (TLS) web protocols.
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New clients from the USPS are required occasionally for mailers to be able to upload the MSP-generated Mail.dat files to PostalOne!.

These changes do not affect MailStream Plus (MSP) itself.   As long as a version of MSP that supports the current USPS regulations is being used, no changes are required to MSP.
UPDATED:  August 21, 2017