Hi, which phrase is more suitable in formal emails?! thank you so much or thanks a lot? and also what about thanks a bunch?! thanks a bundle?!

Hi All I had introduction meeting with a customer's manger, and I prepared a follow up thank you letter: Dear xyz it was a big pleasure to have this fruitiness meeting with you. and in case you needed any support or have any issues you should

Hi All, I'm trying to reach somone(Senior executive) by phone, but with couldnt catch him so I will write the following email: Dear xyz Trust my note finds you well/ (or hope all is well) ?? I tried to reach you by phone via your secretary