Senders Email Address

I’m wondering what the rules are for the Simple Subscribe senders email. If I put in a gmail account, it seems to work just fine. However, when I attempt to put in my company’s email address it says that email has been sent, but emails are never received.
[email protected] = works fine
[email protected] = does not send emails.

Thanks,
Jim

https://wordpress.org/plugins/simple-subscribe/