That’s actually how I use it. My email address, jason -at- hendriks -dot- ca, is a Gmail address.
Jasons-Mac-Pro:plugins jasonhendriks$ dig mx hendriks.ca | grep MX
;hendriks.ca. IN MX
hendriks.ca. 3532 IN MX 1 ASPMX.L.GOOGLE.COM.
hendriks.ca. 3532 IN MX 5 ALT1.ASPMX.L.GOOGLE.COM.
hendriks.ca. 3532 IN MX 5 ALT2.ASPMX.L.GOOGLE.COM.
hendriks.ca. 3532 IN MX 10 ALT3.ASPMX.L.GOOGLE.COM.
hendriks.ca. 3532 IN MX 10 ALT4.ASPMX.L.GOOGLE.COM.
I use the free Google Apps Standard Edition to manage my domains. Unfortunately Standard Edition stopped accepting new users at the end of 2012 and now I think your only Google option is to pay for Google Apps for Work.
Hotmail and Yahoo might have custom domain solutions, but I don’t use their services.
If you don’t want to pay for Google, in your case I would create a new Gmail account for my wordpress site (eg. “[email protected]”), and then I would set the reply-to field (in Postman, and for example in the header section of Contact Form 7) to be my real name and domain (eg. “Joe” <[email protected]>).
Thanks for using the plugin and please give it a rating and review!! ??