What it does
AuthSMTP sends outgoing email from websites, mailing lists and email applications. Its control panel manages sender addresses, domain authentication and two monthly limits: recipient count and total message data. Packages are paid annually.
Count recipients and message size together when sizing AuthSMTP. A message copied to three additional recipients counts as four messages, and its data size is counted four times too. The first quota reached, message count or total data, limits further sending. This matters for a notification stream with attachments even when its recipient count looks modest.
Usage resets in monthly periods measured from account creation. Alerts are sent as either quota approaches exhaustion; at the full allowance, sending stops until the quota resets or the account is upgraded. Check the control panel's reset date instead of assuming the first of the calendar month.
After buying a package, use the activation email to set separate control-panel and SMTP passwords and enter billing details. The setup tool takes you through adding a domain, publishing email authentication records, authorizing From addresses and configuring your application. Send test messages and complete the verification questionnaire. New accounts can send only 30 messages until verified.
These are the three smallest published packages. Each uses a shared IP address.
| Package | Annual price, USD | Monthly emails | Monthly data |
|---|---|---|---|
| AuthSMTP 2 | $72 | 2,000 | 600 MB |
| AuthSMTP 4 | $108 | 4,000 | 1.20 GB |
| AuthSMTP 6 | $144 | 6,000 | 1.80 GB |
They allow 20, 40 and 60 From addresses or domains respectively. AuthSMTP does not offer a free account or trial; it offers a money-back guarantee instead.
Strengths
- Both recipient count and data usage are visible account limits
- Sender addresses or whole domains can be authorized in the control panel
Watch out for
- Reaching either monthly quota stops sending until reset or upgrade
Best for
- Website and mailing-list operators managing predictable SMTP relay usage
Sources
- Authenticated SMTP Email Relay Service | AuthSMTP (Oct 26, 2026)
- Can I use AuthSMTP to send mail from multiple email… | AuthSMTP (Oct 26, 2026)
- How do the message number and size quotas work? | AuthSMTP (Oct 26, 2026)
- Authenticated SMTP Service Pricing | AuthSMTP (Oct 27, 2026)
- AuthSMTP Getting Started Guide (Oct 27, 2026)
- Do you offer a FREE or trial SMTP service? | AuthSMTP (Oct 27, 2026)