Gmail rejection from one Google account on iMac

When I send a gmail from one of my gmail accounts it always comes back. Sometimes with this message:

You have reached a limit for sending mail. Your message was not sent.

Does this message mean I sent too many gmails to this ONE address, or to all, cumulatively?

In my 'settings' I check 'unlimited'.

None of these people are on my block list. Help.

[Re-Titled by Moderator]

Original Title: ALL SENT GMAILS REJECTED FROM ONE GOOGLE ACCOUNT ON IMAC