I've been looking for the whole day for a plugin that help me to solve my problem with my website.
Is there a way to create a specific form that could send a custom e-mail when the user complete it?
There are so many plugins for that :- 1) Contact form 7 2) Ninja form If you want to insert a post or product you can choose gravity form.
it help you to create custom functions. if you want to create/send mail custom then you should try wp_mail ( which is wordpress function ) or php core function is mail(). do proper R & D on it and its parameter also.
parameter also provide you sender info and receiver info.
on submit your form you can use these functions.
reference links for mail functions :-
i hope its help you. thank.