Relationships with clients, namely, are the same as with other people. That's why the rules are the same. You just don't have to rush into it. You have to give the client time to get to know you better, to get to know you without trying to sell you in at once. You should visit https://newmediaservices.com.au/how-to-write-great-customer-service-email/ and study in detail how to write letters and mailing lists to please clients.

Introduce yourself, write who you are and where you are from. The simpler the better. You don't have to tell about your company in your greeting and introduction. Just introduce yourself.

Thank you for the information, there is always a need to learn communication and the opportunity not to go beyond the rules of communication. But the cases are so different that it is sometimes difficult for me to keep my balance when communicating with demanding or simply impolite clients. Sometimes I can't control my behavior so much that I decided to take a test https://us.calmerry.com/tests/ to understand if I need to seek outside help.