Does it matter than I no longer provide happy massages?

It is certainly a possibility, particularly if the person is willing to confirm the emails. It is not too early to retain counsel. Doing so would be in your best interest.

There is not too much you can do about the past. I don't know what is in the email but it is unlikely actionable. If you receive a summons contact me or another attorney immediately. The earlier in the process a lawyer gets involved the better your chance to get it cleaned up with less difficulty.

Do it no more. If the police contact you, do NOT give them a statement no matter what they threaten.

If I understand correctly, what you mean by happy massages, you were in violation of California Penal Code Section PC 647(b) Every person who commits any of the following acts is guilty of disorderly conduct, a misdemeanor: (b) Who solicits or who agrees to engage in or who engages in any act of prostitution. A person agrees to engage in an act of prostitution when, with specific intent to so engage, he or she manifests an acceptance of an offer or solicitation to so engage, regardless of whether the offer or solicitation was made by a person who also possessed the specific intent to engage in prostitution. No agreement to engage in an act of prostitution shall constitute a violation of this subdivision unless some act, in addition to the agreement, is done within this state in furtherance of the commission of an act of prostitution by the person agreeing to engage in that act. As used in this subdivision, "prostitution" includes any lewd act between persons for money or other consideration. The question then becomes can they prove the violation by the emails. The other question is are the emails over one year old. If the violation cannot be proven by the emails or if the violation was over a year ago you are OK.