Do you know of any SaaS products which provide test details / sandbox environments?

I'm trying to pull together a list of SaaS products which provide test details / sandbox environments i.e.

• Payment details to simulate e-commerce transactions i.e. Stripe, GoCardless
• A mobile number to simulate an SMS message being sent i.e. Nemxo, Twillio
• An API key to provided access to limited feature set for evaluation
• A sandbox environment for full simulation of your integration.
• A mailbox you can send an email to in order to check it's potentially spam score.
• etc

Do any of you provide test details for your SaaS products or know of any SaaS products that do?