What does 2 Cor. 5:16 (knowing Christ no longer in the flesh) mean to Paul's Acts ministry?

What does 2 Cor 5:16 mean with regard to believers no longer knowing Christ according to the flesh (according to His earthly ministry) if Paul was yet preaching Him as Messiah in the synagogues...preaching Him according to the flesh?

It's a long context, and we can't isolate this part, so here it is: 2Co 5:11  Knowing therefore the terror of the Lord, we persuade men; but we are made manifest unto God; and I trust also are made manifest in your consciences.
2Co 5:12  For we commend not ourselves again unto you, but give you occasion to glory on our behalf, that ye may have somewhat to answer them which glory in appearance, and not in heart.
2Co 5:13  For whether we be beside ourselves, it is to God: or whether we be sober, it is for your cause.
2Co 5:14  For the love of Christ constraineth us; because we thus judge, that if one died for all, then were all dead:
2Co 5:15  And that he died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again. 2Co 5:16  Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more.
2Co 5:17  Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.
2Co 5:18  And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation;
2Co 5:19  To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation.
2Co 5:20  Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ's stead, be ye reconciled to God.
2Co 5:21  For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.

I think, one died, then all were dead, and henceforth not living for ourselves, but unto Him that died and rose again are contextual defining elements. These are the things said before. Then Paul says, therefore if any man be in Christ he is a new creation, old things have passed away. This is what is said after. Here is the central portion as it were;

2Co 5:15  And that he died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again. 2Co 5:16  Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more.
2Co 5:17  Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.

Flesh and spirit are recurring themes in Paul. Living unto Christ meant he no longer knew any man after the flesh. Knowing Christ after the flesh could mean Paul knew Christ before being in Christ?

In Roms.7 he wanted to serve the Law in newness of spirit, but he was carnal (fleshly). Walking by the Spirit, in newness of life, Roms.8 was how he wanted to know Christ now, being lead by the Spirit and not the flesh, see also Gals. 5.

While this might not explain it fully, and to be sure, this is the best I can do off the top of my head, the passage/context removes any possibility for the unrelated view that this has to do with Christ's earthly ministry.

Stuart Allen's audio number A468 might be helpful, I can't remember its content. ON this page http://www.bibleunderstanding.com/allen4.htm