oops 382 document apisendmail and improve usability

[alexfarrill]

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Checklist before requesting a review

• [ ] I have performed a self-review of my code
• [ ] If it is a core feature, I have added thorough tests.

[vercel[bot]]

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Name	Status	Preview	Updated
mailing-dynamic-demo	✅ Ready (Inspect)	Visit Preview	Nov 30, 2022 at 9:33PM (UTC)
web-emails	✅ Ready (Inspect)	Visit Preview	Nov 30, 2022 at 9:33PM (UTC)

1 Ignored Deployment

| Name | Status | Preview | Updated | | :--- | :----- | :------ | :------ | | **web** | ⬜️ Ignored ([Inspect](https://vercel.com/sofn/web/2bNDNwD9fhrx6MFe8RTBotG3UL56)) | | Nov 30, 2022 at 9:33PM (UTC) |