Please read the following if the sender receives a bounce message that says something like "host mail.yourdomainname.com.au[18.104.22.168] said: 550 Sender verify failed (in reply to RCPT TO command)"
Domain Hosting Shop's servers attempt to confirm the sender of a given piece of mail by verifying that the From: address provided is a real one. For example, if you send a piece of mail claiming to be "From: email@example.com", and you send that mail to "firstname.lastname@example.org", our mail servers contact the servers at "bluewidgets.com", to confirm that "bob" really is a valid mailbox there. If the return address proves to be false, the mail will not be accepted by our servers.
When an email is rejected, the sender is sent a bounce email telling them that the verification attempt failed. The only solution for this is for the sender to use a real working return address on mail that is sent to our mail servers. For example, if you sent mail out with the "From:" address of "BlueWidgetsBob" instead of your real mailbox name of "email@example.com", that could cause sender verification to fail. Always use your real return address in e-mails if you want them delivered.
Sender verification is a major way to stop the constant inflow of SPAM. Unfortunately it's configured at server level, so cannot be turned on or turned off so that you can receive an email. It also cannot be turned on or off on a per-domain basis.
If you really want to receive an email from someone that's trying to send something to you, get them to send it to your hotmail or gmail address. DHS servers provide mission critical uptime, and sender verification is one of the many things that allows us to do so.