SMTP stands for Simple Mail Transfer Protocol. It is the set of rules that email servers use to pass messages to each other. Every time you send an email, whether from Outlook in St. George’s or from a booking website in Carriacou, SMTP carries it from your side to the recipient’s mail server.
How it works, step by step
- You press send. Your email app or website hands the message to an outgoing SMTP server.
- The server looks up the destination. It checks the domain after the @ sign, for example gmail.com, and finds that domain’s mail server through DNS.
- The servers talk. Your SMTP server connects to the recipient’s server, identifies itself and passes the message across.
- The recipient’s server decides. It checks the sender’s reputation and authentication, then places the message in the inbox, the spam folder, or rejects it.
- The reader collects it. The recipient’s app downloads the message using a different protocol, such as IMAP or POP3.
Why website email often goes missing
Many Grenadian websites are hosted on shared servers abroad. By default, they send email from the hosting server itself. That server may share its IP address with thousands of other sites, some of them sending spam, and often lacks proper authentication for your domain. The result: contact-form notifications, order confirmations and booking emails land in spam or disappear.
What an SMTP relay changes
A dedicated SMTP relay like Mailpro’s SMTP server takes over the sending. Your website connects to Mailpro with a username and password, and Mailpro delivers the message through infrastructure managed for email, with deliverability routing and full tracking.
Key terms
- Port: the “door” used to connect, commonly 587 or 465 for authenticated sending.
- Authentication: the username and password your software uses to connect.
- TLS: encryption that protects the message in transit. Mailpro supports TLS 1.3.
- SPF, DKIM and DMARC: DNS records that prove your domain authorised the sending server. They help your email reach the inbox and protect your brand from spoofing.
- Bounce: a message returned because the address doesn’t exist (hard bounce) or is temporarily unavailable (soft bounce).
SMTP and the law in Grenada
SMTP itself is neutral, but how you use it matters. Grenada’s Electronic Crimes Act, 2013 treats sending multiple emails with a counterfeit source or falsified header information, with intent to mislead, as an offence. Sending through an authenticated relay under your own domain keeps your messages honest and traceable. For marketing emails, consent rules still apply to your recipients; see our Grenada email law guide.
SMTP or API?
If your software has an SMTP setting, it is usually the fastest route. If you are building a custom integration, an API may suit you better. Compare them in API vs SMTP.
SMTP, IMAP and POP3: what’s the difference?
SMTP sends email. IMAP and POP3 are used to read it. IMAP keeps messages on the server so you see the same inbox on your phone and computer; POP3 downloads them to one device. When you set up an email account on a new phone, you usually enter settings for both: SMTP for outgoing mail and IMAP for incoming mail. An SMTP relay like Mailpro handles only the outgoing side.
How to tell if your email is authenticated
Open an email you sent in Gmail, choose “Show original,” and look for “PASS” next to SPF, DKIM and DMARC. If any show “FAIL” or are missing, your domain needs attention before you rely on it for important messages.
Mailpro has operated email infrastructure from Geneva since 2001, with data hosted in Switzerland outside US jurisdiction. See pricing to get started with 500 free credits.