Why is Verification Necessary?
With the increase of spam, email providers such as Yahoo, Gmail, Hotmail, etc are trying to protect their email users. Because of this they are blocking more and more legitimate emails as well. Recently Yahoo implemented a new security measure that affects all yahoo addresses. You can read more about that here: https://help.yahoo.com/kb/mail/SLN24016.html?impressions=true
Does this Affect Me?
If you have an email using a public domain such as '@yahoo.com', '@gmail.com' or '@hotmail.com' you are likely affected or will be soon. Yahoo has implemented this security and the others are likely to do so soon.
What Can I do?
We strongly recommend that our clients get an email address using their own website domain, such as 'email@example.com'. This not only looks more professional to your clients, but also allows you to verify things and increase your email deliverability.
I have my Email Address, Now What?
Once you have your email address, you can go to the Admin module -> Setup -> Getting Started -> Email Settings & Verification page to begin the verification process. Click on the 'Add My Signature' link. That will add your signature to our email provider. Then you need to get the SPF and DKIM records and put them into your domain name DNS file. How you do that depends on who you have registered your domain name through. You can contact them for more information on how to create the needed records.