If you're trying to set up your custom e-mail and have seen the following error, 'You can't use public domain emails'... Then please read on.
You cannot use a public domain email (Gmail, Yahoo etc.) as your custom e-mail address. This is for one simple reason, you cannot modify their DNS settings. You must use a privately owned domain as you're sending email: i.e.: email@example.com
If you have previously tried to generate an email signature using a public domain email, then you will need to do a couple of things before you can add your own personal domain to your email signature.
First of all click here: https://app.nusii.com/settings/my_info
Update to your desired email address and then go to: https://app.nusii.com/settings/email_signature.
Disconnect your previous email signature and begin the process again using your desired custom email address.
Please note that any changes made to your DNS can take up to 48 hours to be reflected. This is out of our control. If your email still hasn't been verified after this time, please contact us and we'll do our very best help you.