Hello @CeceliaR67 ,
If you're using a free email domain (e.g. gmail, yahoo, aol, live, icloud, etc.) to send your emails, your only option would be to use the ccsend rewrite for general authentication, since you have no control over that domain and it's a widely available one.
If you have your own domain for your organization, then whomever you purchased the domain from or setup your website and email system through should have further insight on plugging in the self-authentication information we provide. I would advise referring to our Community's Self-Authentication FAQ for additional info, and links to the relevant guides and articles.
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