SMTP, the Simple Mail Transfer Protocol, is the standard that moves email across the internet. Whenever someone in St. John’s sends a message to a client in Toronto, SMTP carries it from the sender’s mail server to the recipient’s. You rarely see it, but every email depends on it.
How a message travels
- Your email program or application connects to an outgoing SMTP server and hands over the message.
- The server looks up where the recipient’s domain receives mail (its MX record).
- It connects to that receiving server and delivers the message.
- The receiving server checks the message, including authentication, and places it in the inbox, the spam folder, or rejects it.
SMTP only sends. Reading email uses other protocols, IMAP or POP3.
Ports and encryption
Applications usually connect on port 587 with STARTTLS or port 465 with implicit TLS. Port 25 is used between servers and is often blocked for ordinary connections. Mailpro’s FAQ on which SMTP port to use and the blog comparison of ports 465 and 587 go into detail. Mailpro supports TLS 1.3 for encrypted connections.
Why businesses in Antigua and Barbuda need to care
Many local websites, booking systems and point-of-sale tools send email through the default mail server of their web host. That server is often shared with many other sites, has no reputation management and lacks proper authentication. The result: booking confirmations in guests’ spam folders, password resets that never arrive, and invoices that clients say they did not receive. For a tourism business whose guests are overseas, a missing confirmation email can mean a worried phone call or a cancelled booking.
SMTP relay: the fix
An SMTP relay is a specialised outgoing server that your software uses instead of the default. Mailpro’s SMTP server is one. It adds:
- authenticated sending with SPF and DKIM;
- bounce processing and retries;
- delivery statistics per message;
- a sending reputation built for volume.
The blog explains the idea further in what is an SMTP relay.
Authentication in one paragraph
Receiving servers ask three questions. Is this server allowed to send for this domain? That is SPF. Was the message signed by the domain and left unaltered? That is DKIM. What should happen if the first two checks fail? That is DMARC. Without them, even genuine messages from an Antiguan business can look like forgeries, and Gmail and Yahoo now expect them from anyone sending in volume.
Data protection angle
Every email passing through an SMTP server contains personal data: at least the recipient’s address, often much more. Antigua and Barbuda’s Data Protection Act, 2013 makes you responsible for protecting that data, including when a processor handles it. Choosing where your relay is hosted is part of that decision. Mailpro’s servers are in Switzerland, outside US jurisdiction.
Setting it up
You need four values from Mailpro: server name, port, username and password. Enter them in your application’s outgoing mail settings, add the DNS records for authentication, and send a test. From then on, track results in SMTP statistics.