How to avoid getting into spam?

Question

Mail server

I have a directory of reliable service providers. I would like to place a form on my site in which the visitor can select a list of suppliers of interest to him and send them the same letter in bulk.

What is the best way to implement this so that such letters do not fall into spam?

Send a letter from the mail of my site or substitute the visitor's email when sending?
What other conventions must be observed in order for this service to continue to reliably deliver letters to suppliers and not fall into spam?

Answer 1

The most important condition for not being included in the spam list is not to send spam.

Answer 2

By default, almost everywhere, there are filters of various kinds for spam.
And if your email is not registered in the phone book, then 50/50.
Just go with that number.

Answer 3

It would be best to make a separate domain of your site for mailing, so that in any case it would not directly affect the sending of letters from your site. No one will reveal the exact mechanics of how to bypass spam, but there is an interesting article that will help with this.
In any case, if the letters are undesirable for the recipient, or the user of the form even wants to use sending from such a form for their advertising fraud, nothing will help here.