Yes. You can add email addresses or domain to your mailbox 'Trusted Senders' list. This will mean that emails received from this address or domain will bypass Greylisting and other Spam filtering.

To add an address or domain to your 'Trusted Senders' list please log into the webmail interface for your mailbox at http://mail.yourdomain.com/ (where 'yourdomain.com' is the domain you wish to access).

Once logged in select the 'My Spam Filtering' within the 'Settings' menu. Click the 'Trusted Senders' tab and enter the required address(es)/domain(s). Click save.