I followed the instructions at the following link, until I got stalled at Section 2, sub-section 4 ("Check the validity of the Domain Key")  https://www.zoho.com/mail/help/adminconsole/domain-keys-configuration.html . Here is a screen shot of the failure.

I contacted my domain hosting company (Dreamhost). They had a look at my settings and said that everything seems to be in order at their end, and that I'd need to contact Zoho to find out if I am indeed typing in the correct things.

Here is a screenshot of what I typed in my Dreamhost control panel:

Here is a screenshot of the text that Zoho provided to me:

Can anyone identify the problem?