Email Accounts / Setting / Should it be external (Gmail) or Zoho?

Email Accounts / Setting / Should it be external (Gmail) or Zoho?

I'm confused.

When I registered, I entered my Gmail address to receive my new account confirmation notice from you.  I clicked the link and successfully activated my account.

Under Accounts, I saw that my "Primary Email ID" was Gmail, and not sure why that is, I changed it to my new Zoho account, which I may use as my primary email account universally.  So, I added it and made it my new "Primary Email ID".

While exploring, I found myself in "Accounts", and under "Email Accounts" I noticed mention that this is where I would be notified if there is a problem with my account (such as inability to login, I assume).  So, I'm thinking it probably should be an external email address after all, so I changed it back to my Gmail account.

Now, I see my Zoho account listed as my Gmail address, notably at the top right of the Accounts page.

Please explain the Primary and Secondary Email ID accounts settings, what purpose these listed accounts serve, and whether I should have as my primary my Gmail or my Zoho account.

Thank you,

Kevin

P.S.  Terrific service!  Just discovered it yesterday, and am very impressed so far!