If your email address does not match your company domain, your account can still be connected to your company.
1. Create your account (to learn more about how to create an account, read How Do I Create A User Account?) After you have created your Handshake account and confirmed your email address, you will need to connect to your company profile.
2. If your organization is already using Handshake, search for it by name using the find and join your company which will appear during the account creation process.
3. When your company’s name appears, you can select Request and then Next: Connect to Schools to submit your request and continue your registration. 
Complete the registration process by selecting the Schools you're interested in recruiting at, and click on Finish at the top of the page.
Since you have a different domain name than the the company you are joining, your account will be placed in a “pending status” until you are manually approved by the Owner of the company profile. To learn more about what it means to be in Pending status, read What is a "pending" status at my company?