Do the email addresses use the domain name of your email provider, or do they use the domain name(s) of your websites?
>they use the name of my websites
Then you can set up your own SMTP server, just like you set up your own web server. Just tell your DNS nameserver to send mail to your SMTP server. It's a bit of a learning curve to setup, but you'll know that you have control over your own mail server and you won't be at the mercy of some tech company.
Well known SMTP servers in the Unix/Linux world include Sendmail, qmail, Exim, and Postfix. And there are many others. Here's a list:
Also, you may need to have the ISP set up reverse DNS lookup for the server's IP.
ISP=internet service provider
DNS=domain name system
IP=internet protocol (address)
@Pat they use the name of my websites