letter/email/message. You may also use "etc." which is commonly used even in formal contexts. However in my opinion, it is as vague as "as so on". An alternative would be to list out a few examples of what you are talking about then add "and many other ___". For example: "At...
A query letter is a letter asking an editor if he or she would consider accepting a work of writing for publication consideration. You need to describe the work in question well enough to give the editor a good idea of what it is about. 4 Use email to contact human resources. If you...