Useful expression for Emails:

Note: Styles which have been mentioned as ‘Semi-formal’ and ‘Business friendly’ are preferred in interaction with customers.

Function Style and Use
Address
Dear James Used with Semi-formal relationships and contexts; can we used with someone you haven’t met
Dear Mr. Mason Formal relationship and contexts; Often with people you haven’t met
Dear Mr. James Mason Very formal relationship and contexts; Used in legal notifications and letters
Dear Ms. Melissa Formal
Dear Associates Formal with Business Partners
Hi Melissa Semi-formal and Business friendly
Hi James Semi-formal and Business friendly
Hello James Semi-formal and Business friendly
Melissa For conversational threads, frequent interactions, and within teams
Mel Very familiar and casual, only with people you are very familiar with and in informal context
Jim Very familiar and casual, only with people you are very familiar with and in informal context
Hi Semi-formal but impersonal and matter-of-fact; use with more than 3 addressees
Hi Everyone/Everybody/All Semi-formal; with groups
Hi guys and gals! Very casual; only with close friends and for personal messages
Hi Ladies! Only for casual messages and between women preferably!
Signoff
Speak to you soon Informal
Looking forward to hearing from you Informal and Personal
I look forward to hear from you Informal and Personal
Kind Regards/Best Regards/Warm Regards/Wishes Semi-formal
All the best Informal
Sincerely Yours Very formal and old-fashioned (Don’t use)
Thanks Informal
Regards Semi-formal
Thanks and Regards Semi-formal
Cheers With British Colleagues and Clients
Have a nice day/Wonderful weekend Informal