After any meeting, success, or comment, it will never hurt to follow the thank you note. It shows that it respects customers' time and even if the product is not good at this time, your client knows he is a polite, professional associate with whom he wants business.
Email or snail message? You know best; Think of the client's corporate culture. In general, emails are ok, especially if they are thankful for something informal like time.
Your voice is just something you can measure. If you have any doubts, the more formal is the better. Do not need to be cold or fussy, but respectful
Here are some examples of customizing your own situation.
I was pleased to meet you yesterday. Your ideas about new approaches to sales within your region have gained insight and have helped me a lot. Thank you for saving me time and sharing your thoughts.
————————— ————–  Dear Dr. Price,
Thank you for seeing me yesterday. I appreciated the chance to discuss our new products with you. Your opinions are always useful and interesting. I hope the latest product meets your needs.
I'm always happy to see you.
——————– ———————  Josh,
It was a pleasure to finally meet you today. The research project seems to be very interesting and offers stunning value for mobile phone service providers. As I have already discussed, my team has carried out extensive work on the type of data collection required for research.
Please let me know if I can provide more details on how we will work on the project.
will talk to you soon.
—————————————–  Dear Paul,
Thank you for your time. Jack and I appreciated your views on your new business development strategy. I know that you now have many demands on the timetable, so you can have more greetings than you did to us.
We are confident that we will return with you when the plan is finalized in order to provide your approval stamp and final comments.