Explanation of How The Holy Spirit Is A Part of The Trinity

Continued from Part 33

Leaving out reference to the holy sprit
In the opening salutation of Paul’s letters to various churches (Romans through Thessalonians) he sends personal greetings from “God the Father and the Lord Jesus Christ.”  If “the Holy Spirit” were an integral and personal part of a triune deity, then why does He not send His personal greetings as well?