Binary package “postsrsd” in ubuntu xenial

Sender Rewriting Scheme (SRS) lookup table for Postfix

 PostSRSd provides Sender Rewriting Scheme (SRS) support for Postfix via
 TCP-based lookup tables. SRS is needed if your mail server acts as a forwarder,
 and the mail originates from a server with Sender Policy Framework (SPF)
 enabled.