The default Send Email action without using your own Sendgrid API key is purely meant for development.
When you’re not using your own Sendgrid account, you’re subject to rate limits and the reputation of Bubble’s shared Sendgrid account (which isn’t very good). When you have a bad sending reputation, most of the time your emails won’t be delivered, especially with Outlook, Hotmail, or any Microsoft-owned emails.
I would recommend either:
- Using your own Sendgrid API key or
- Use Postmark (here’s why: Postmark is awesome)