Sending from where you already build
Most of these tools can already send mail, through a mailbox you connected or through the platform's own infrastructure. That holds until something depends on it arriving. Then you want a domain you control, a signing key that is yours, and a record of what happened to each message — which is the same API call everywhere, and a different five minutes of setup in each tool.
Send email from Bubble
BubbleAPI Connector, one POST call, and a shared header your other calls can reuse.
Send email from Make
MakeOne HTTP module, and a scenario that can branch on the reply instead of guessing.
Send email from Retool
RetoolOne REST API resource, reused by every query that needs to send something.
Send email from n8n
n8nHTTP Request node with a Header Auth credential, so the key never sits in the workflow.
Sending from Lovable and Supabase
LovableA working Edge Function, and why SMTP is the wrong tool inside one.
Somewhere else?
Anything that can make an HTTP request can send through us, and the request is the same one in every guide above. The API reference has it, and the SMTP settings cover tools that only speak SMTP.