SMTPKeepHigh Volume Email or an SMTP relay?
Microsoft's High Volume Email (HVE) is a sending service inside Exchange Online for apps and devices. It suits some scanners and not others.
| High Volume Email | SMTPKeep | |
|---|---|---|
| Recipients | Internal recipients in your tenant only | Anyone, inside or outside |
| Device login | Basic auth or OAuth to smtp.hve.mx.microsoft, port 587 | Username and password to smtp.smtpkeep.com |
| Price | $42 per million recipients, pay-as-you-go billing since June 1, 2026 | $10 per tenant per month |
| Limits | Up to 100 HVE accounts, 50 recipients per message, 10 MB messages | Your mailbox's Graph sending limits |
| Old TLS | No | TLS 1.0 and 1.1 on port 2525 |
Use HVE when
A device only ever emails staff, for example scan-to-self or internal alerts, and you already have pay-as-you-go billing set up.
Use a relay when
Scans or app mail go to customers, vendors or anyone outside the tenant, or the device only speaks old TLS.
HVE details from Microsoft Learn and Message Center post MC1243552, as of October 2026.