What are the differences among the below types of e-mail? a) Email to customer b) Email to line manager c) Email to vendor d) Email to friend

Thanks 

A- email to customer is a general e-mail we use it to inform him-her for new services,products and maintain the connection process with customers 

B- with line manager is an official e-mail to brief and detailed him-her according to achievements, performance, issues related. To work, tasks accomplished, other duties related to work and company 

C- we need to contact vendor when we asking for contracts, complains from customers, new offer, debts, ...

D- to friend this is unofficial e-mail we need to send it occasionally when our friends have birthdays, anniversaries,..

I agree with our expert - Mr. Omar Saad. Thanks for inviting!

The purpose of email is to communicate message. Some messages are for action and some for information. All the messages shall have appropriate and attractive subject heading.  Salutation, content, closing remarks may differ based on standard criteria to whom it is addressed. 

Thank you for the invitation

Thank you for the valuable information and useful

the differences among these types of e-mail depend on the formal speech 

in business we have to write in a formal ways 

Thank you for invitation. I agree with experts answer & I looking forward new experts answer. 

first 3 are official communication should be done in professional way. last one is a personal communication.