A question of using a P.S.

Today a client asked an interesting question, one that I had not really considered before. The client's question was:

I was hoping I could ask you a quick question regarding email etiquette.

Is it OK to us a “P.S.” on an email?

For instance:

++++++++++++++++++++++++

Sincerely, Ashley

 P.S.  I wish you a very happy Thanksgiving

+++++++++++++++++++++++++

 Or is it best to just include that in the body of the email and not use Post Script??

 Thank you Stephanie!!!

To which I replied:

Well, that's an interesting question and one I've not been asked before.
Here are my thoughts on this:
- marketing studies show that letters with P.S. get more responses than those without
- my personal preference in using the P.S. in clients' letters is to a) add a teaser that begs further questions OR b) address a mundane aspect of the job posting, for example, I possess a valid driver's license with no demerit points in the last 10 years. (using precisely the phrasing found in the job posting)
As for using it in email, as generally email is even less formal than a letter, I see no issue with it. Having said that, you're bound to run across a person, now and then, who detests the "P.S." and likely for personal reasons (someone s/he didn't like used these with wild abandon, for example!). But I've not read anything that should give you concern.
Now back to the P.S. as a marketing idea: remember that your job search is a self-marketing exercise. Use the P.S. to your advantage by selecting a workplace accomplishment that would be intriguing to the reader. For example, aligned with your role and career goal, of course, a story about saving a failing account, restoring a failing or finding a lucrative new product line, achieving consensus where no one else had managed to do so, repeatedly supporting failing students to success ... these kinds of teasers are useful post scripts that will leverage the marketing tool to your benefit.
Here's an example of one I used for a recent client:
By the way, I would love to tell you the interesting details of how I conceived and led an initiative to save our company's most critical account, saving $Millions in potentially lost annual revenues. 
Although this idea is not for everyone, and I don't actually use it for many clients, it can be a powerful tactic to generate interest and to differentiate you from your competition.
All the best, Stephanie
P.S. Last year I helped a European living and working in a war-torn country abroad overcome many odds to land his first Canadian job without having to move here first. Imagine what I could do for your job search! Just sayin' ... :-)