Many domain emails for example joe.schmoe@mybusinessname.com block unsolicited emails that it doesn't recognize. Sometimes the block/filter is through your system's protection software (i.e. McAfee), therefore, you should contact your IT department, have them turn off the blocking/filtering to allow the permitting@rentonwa.gov email to come through to your email box as well as have your IT department add it to your Whitelist.
If you are still having difficulty registering with your domain email address (joe.schmoe@mycompanyname.com), you can register with an email that uses @yahoo, @gmail, or @comcast, etc. Once you have completed the registration process you can then login, go into your My Account and change the email address associated with the registered user account to your company email address.