One of the first things I learned from Mr. Anand Jayaraman, PMP was about this usage of gratitude. I was replying to a UK based client with “Thanks a lot” and he warned me not to use this. I used to get appreciation from my managers about the style of formal mails I write and few clients directly told me the way I explain details via mail are excellent. His comment made me uncomfortable as I use this often for communications both verbal and written. Since I was curious, I asked him directly why I should not be using this and this is one of the most common line we use in conversations.
He explained me, “Thanks a lot” is typical Indian English usage and most people who follow British English (UK) may not follow this and they might think “Thanks, but expecting some more” . He recommended to use "Thank you” or “Thank you very much” depending on the density of gratitude required.
Culture and Project Management
This is how cultural difference plays differently in project management deals. It is important to respect and comply cultural differences when managing overseas projects/clients/suppliers/team members etc. You will have to follow the rules of land.
Eg: when you get a project from another country, it is good to learn cultural differences and customs before you really start communicating to those customers.