Service Manager supports a simple SMTP connection to an outgoing mail server. No security protocols are supported.
That means your ISP email server is required to send out email. However, the email server used to send mail does not affect your reply address which should be your normal business address.
Example: A Comcast or Cox cable SMTP server is used to send out the notifcation email while the return address email is your business domain address or a gmail account.
If there are any issues with sending a test email in Service Manager check with your ISP support desk to confirm no security protocols are required (since you are already on their network).