SMTP Relays & Deliverability
Improve email deliverability by routing outgoing mail through a professional SMTP relay service.
When you send email from your Havenoro CP server, it normally goes directly from your server to the recipient's mail server. This works well for low volumes of personal email, but for larger volumes or when you need guaranteed delivery, using an SMTP relay is a much better approach.
What is an SMTP Relay?
An SMTP relay is a third-party service that sends email on your behalf. Instead of your server delivering the message directly to the recipient's mail server, it hands the message off to the relay service, which then delivers it. Think of it like a courier service for your email.
Here is an analogy: If you move to a new neighborhood, people do not know who you are. If you try to deliver packages yourself, recipients might be suspicious and turn you away. But if a well-known, trusted friend (the relay) delivers the package on your behalf, it is much more likely to be accepted. SMTP relay services have established reputations with major email providers like Gmail, Outlook, and Yahoo. When they deliver your email, it is more likely to land in the inbox rather than the spam folder.
Why Use an SMTP Relay?
Your server has an IP address. That IP address has a reputation. If your server is on a shared hosting plan, your IP might be shared with other users, some of whom might send spam. This tarnishes the IP's reputation, and email from that IP — including your legitimate email — is more likely to be blocked or flagged as spam.
SMTP relay services solve this problem because they have:
- Dedicated or high-reputation IPs — carefully managed and monitored for spam
- Established relationships with major email providers
- Delivery optimization — they know how to format, rate-limit, and retry deliveries for maximum success
- Analytics — you can track opens, clicks, bounces, and spam complaints
| Direct delivery (Exim) | SMTP Relay | |
|---|---|---|
| Deliverability | Good for low volumes | Excellent — established provider reputation |
| IP reputation | Your server's IP (may be shared) | Provider's high-reputation IPs |
| Best for | Personal email, low-volume transactional | Bulk mail, marketing, critical transactional |
| Cost | Free (included) | Usually paid (many have free tiers) |
When You Need an SMTP Relay
For most personal or small business email, the default direct delivery works fine. Consider using an SMTP relay in these scenarios:
- Sending more than 100 emails per day — mass mailings from a shared server IP can trigger spam filters and get your server blacklisted.
- Marketing or newsletter emails — email marketing requires high deliverability, analytics (open rates, click rates), and professional unsubscribe handling.
- Transactional emails — order confirmations, password resets, and receipts must arrive immediately and reliably. A relay ensures they do not get caught in spam filters.
- Contact form emails — if your website has a contact form, those emails are often flagged as spam because they appear to come from your server rather than from a known sender. A relay fixes this.
- You have noticed your emails going to spam — if recipients tell you your emails are landing in their spam folder, a relay is usually the solution.
Understanding Ports: 587 vs 465 vs 25
When configuring an SMTP relay, you will need to specify a port. Here is what each port is used for:
| Port | Encryption | Usage |
|---|---|---|
| 25 | None (plain text) | Traditional SMTP port. Often blocked by ISPs and cloud providers to prevent spam. Do not use this for relaying. |
| 465 | SSL/TLS (implicit) | SMTP over SSL. The connection is encrypted from the start. Widely supported and recommended. |
| 587 | STARTTLS (explicit) | SMTP with STARTTLS. The connection starts unencrypted and upgrades to TLS. Also widely supported and a good alternative to port 465. |
Port 25 is often blocked by ISPs and cloud hosting providers because it is the standard port used by spam bots. If your relay provider supports it, use port 465 or 587 — both are secure and typically unblocked. Most SMTP relay providers (SendGrid, Mailgun, Amazon SES) support both 465 and 587.
How to Configure in Havenoro CP
Setting up an SMTP relay in Havenoro CP is done per mail domain. You can use different relays for different domains, or use the default Exim delivery for some domains and a relay for others.
Open the mail domain settings
Go to the Mail tab. Hover over the domain you want to configure and click the Edit icon (pencil).
Enable SMTP Relay
Scroll down to the SMTP Relay section and check the box. A form will appear with fields for the relay configuration.
Enter relay credentials
Fill in the details provided by your relay service:
- Hostname — the relay provider's server, e.g.,
smtp.sendgrid.net - Port — typically
587or465 - Username — your relay account username or API key
- Password — your relay account password or API key
Test the configuration (if available)
Some versions of Havenoro CP include a Test button to verify the relay connection. If not, send a test email and check the headers for relay-specific information.
Click "Save"
Click Save in the top right corner. All outgoing email for this domain will now be routed through the relay.
Next Steps
After configuring your SMTP relay, make sure your email authentication is up to date:
- Update your SPF record to include the relay provider's sending IPs. Most providers publish their SPF include information in their documentation.
- Enable DKIM — even though the relay sends the email, DKIM proves it came from your domain. Configure DKIM in your relay provider's dashboard and add the DKIM TXT record to your DNS.
- Set up DMARC with a
p=quarantinepolicy to protect your domain from spoofing. - Monitor your deliverability using the relay provider's analytics dashboard and tools like Mail-Tester.
For more on email authentication, see the Spam & Filtering tutorial.