Form in multisite

Hi, I need to make a setup like this:

I have a network of sites, and I would like that each site has a contact form addressed to admin for each site (one site per user).
Now create a page with their respective form (http://premium.wpmudev.org/blog/how-to-build-your-own-wordpress-contact-form-and-why/)

So far so we’re good.

What happens is that each user creates a new blog which has different email servers (gmail, outlook, etc) and the configuration of the plugin (superadmin) SMTP host is “mail.mysite.net” (dreamhost server).

As I can do to make this not a conflict with the email servers of the other users.

hope you understand despite my bad English.

thanks!

https://wordpress.org/plugins/wp-mail-smtp/