All glossary entries
Glossary
ESP (Email Service Provider)
The infrastructure provider that actually transmits your email. SendGrid, Amazon SES, Postmark, etc.
ESPs are the wholesale layer of email — they own the IP addresses, the SMTP servers, and the relationships with mailbox providers. Cold outreach platforms (BoomSauce, Apollo, Lemlist, etc.) sit on top of one or more ESPs.
BoomSauce defaults to SendGrid (Twilio) but supports tenant-provided SMTP credentials for direct-from-Google-Workspace or M365 sending.