SMTP Relay (SmartHost)

What is SmartHost and when do you need it?

SmartHost is an SMTP relay server: instead of your server or application trying to deliver email directly to the recipient, it connects to the relay with authentication and the relay takes over delivery on its behalf. You need SmartHost if any of these apply:

• Your mail lands in spam: the IP address of your VPS or dedicated server is new or has a poor reputation with receiving providers; messages are rejected or go to the junk folder.
• Your provider restricts port 25: many cloud and server providers block direct outgoing SMTP traffic to prevent spam.
• You hit your hosting plan’s sending limit: your online shop exceeds the hourly limit in busy periods.
• You want to separate application mail from staff accounts: your CRM, ERP, invoicing software or form plugin currently sends using an employee’s password.
• You cannot see what gets sent: there is no report to show which messages were delivered and which bounced.

What is included in the SmartHost plans?

Every SmartHost plan includes authenticated sending on ports 587 and 465, ready-made SPF and DKIM configuration, and sending reports; the plans differ in monthly sending volume, the number of sender domains and extra features.

The exact monthly sending volume and number of sender domains are kept up to date on the plan cards on this page. Volume sets the plan’s per-account limit; messages above the limit may be held until the next period or rejected. That is why we recommend choosing your plan based on your busiest month.

What are the SmartHost connection settings?

To connect to SmartHost, enter the relay address, port 587 (STARTTLS) or 465 (SSL/TLS), and the username and password from the panel in your application’s SMTP settings. The relay address and credentials are shown in the customer panel under My Services → SmartHost; RELAY_ADDRESS below is only a placeholder.

On port 587 the connection starts in plain text and switches to encryption with the STARTTLS command; on port 465 the connection is established over TLS from the start. Choose “TLS” and “SSL” in your application’s settings according to this pairing; a mismatch is the most common connection error. Relaying over port 25 without authentication is not possible.

Which software and systems work with SmartHost?

SmartHost works with any software that lets you enter an outgoing SMTP server: Linux mail servers, control panels, web applications, desktop programs and even scanning printers. The most common scenarios:

• Postfix: with the relayhost setting and SASL authentication, all of the server’s outgoing mail goes through the relay.
• cPanel / Exim: configure Exim in WHM to use the relay as its smarthost.
• WordPress and WooCommerce: an SMTP plugin sends order and form mail through the relay.
• Laravel, PHPMailer, Node.js and .NET applications: enter the relay details in the application’s SMTP configuration.
• Printers, scanners and monitoring systems: devices that email scanned documents and server alerting systems.

For example, a Laravel application’s .env settings:

MAIL_MAILER=smtp
MAIL_HOST=RELAY_ADDRESS
MAIL_PORT=587
MAIL_USERNAME=username_from_panel
MAIL_PASSWORD=password_from_panel
[email protected]

Whatever software you use, pick the sender address (MAIL_FROM_ADDRESS or its equivalent) from a domain you have authorised in SmartHost. Store the password in an environment variable or the software’s secret settings field, not in source code, so your credentials are not exposed when the repository is shared. After saving the settings, send yourself a test message and check that it appears in the sending report.

How do you set up SPF, DKIM and DMARC for deliverability?

For mail sent through SmartHost to reach recipients reliably, your sender domain needs an SPF record that authorises SmartHost, the DKIM key given in the panel and a DMARC policy. “SPF and DKIM ready” means the signing infrastructure on the relay side is in place and the records you need to add are prepared for you; adding them to your domain’s DNS is up to you.

1. SPF: add the include mechanism shown in the panel to your existing SPF record. If your domain already uses a mail service (for example business email), combine both in the same record; two separate SPF records break validation.
2. DKIM: add the public key as a TXT record under the selector name shown in the panel.
3. DMARC: start with v=DMARC1; p=none; rua=mailto:... and tighten the policy once the reports show every legitimate source passing.

For DMARC to pass, the domain verified by SPF or DKIM must align with the domain in the From address the recipient sees. Choosing a sender address on a domain you have not authorised breaks that alignment.

How do you plan sending limits and volume?

SmartHost plans are split by monthly sending volume and every account has a sending limit; the right plan covers the total number of emails in your busiest month with a safety margin. When estimating volume, count:

• Transactional mail: order confirmations, shipping notices, invoices, password resets and sign-up verification. These grow in step with your orders and members.
• Notifications: form notifications, system alerts and automated reports from your admin panel.
• Campaign periods: on sale days, orders and the mail that comes with them can multiply several times over.
• Recipient count: if a message has several recipients, each recipient counts as a separate send.

If you send bulk announcements or newsletters, spreading the sending over time protects both your limit and the receiving providers’ rate limits.

Why do bounce management and list hygiene matter?

Bounce management means detecting addresses that cannot be delivered to and removing them from your list; sending to invalid addresses again and again quickly ruins your sender reputation with receiving providers. There are two kinds of bounce:

On plans with bounce management, bounces are processed and reported separately; on other plans you can do the same clean-up yourself by checking the sending reports regularly. For list health, also:

• Use email confirmation (double opt-in) at sign-up so mistyped addresses never enter the list.
• Keep addresses with no engagement for a long time in a separate segment.
• Never send to bought or scraped lists.

How do you use sending reports to troubleshoot?

Sending reports show whether each message passing through SmartHost was accepted, delivered or bounced; they are the first place to look when a customer says they never got an email. Read the report in this order:

1. Did the message reach the relay? If there is no record at all, the problem is on your application’s side: SMTP settings, authentication or a firewall.
2. Did the receiving server accept it? If it shows as delivered, the message reached the recipient’s server; ask the recipient to check spam and other folders.
3. If it bounced, why? The response code in the error text points the way: 5xx codes mean permanent rejection, 4xx codes a temporary problem. Error text mentioning SPF, DKIM or DMARC points to your DNS records.
4. Is it concentrated on one provider? If rejections happen only at one receiving provider, look at the content or that provider’s rate limits.

If you cannot solve it, include the relevant line from the report and the recipient address in a support ticket so the problem can be traced quickly.

When do you need a dedicated IP?

A dedicated IP means your SmartHost mail leaves from an IP address used only by you; it makes sense for businesses that send regular, high volumes and want to manage their sender reputation entirely through their own behaviour. It is offered on the top plan.

The advantages of a dedicated IP, and what to watch out for:

• Reputation is in your hands: other senders’ behaviour does not affect your IP’s reputation; with a good list and regular sending you build a strong one.
• It needs warming up: sending high volumes from a new IP on day one looks suspicious. Increase volume gradually over a few weeks.
• Consistency matters: with a pattern of one heavy send a month and silence the rest of the time, a dedicated IP never builds a stable reputation; at low, irregular volumes the shared pool usually performs better.
• The responsibility is yours: the quality of your list is reflected directly in your IP’s reputation.

We recommend agreeing reverse DNS (rDNS) and other technical details for a dedicated IP with the support team before ordering.

SmartHost or your own SMTP server?

Running your own SMTP server gives you full control, but also makes you responsible for IP reputation, blacklist monitoring, TLS certificates, the PTR record, queue management and security updates; SmartHost takes these jobs on with ready-made infrastructure and leaves you only the connection settings.

• SmartHost makes sense if email infrastructure is not your core business, if your server’s IP is new or has a poor reputation, or if you want a fast solution with reporting.
• Your own server makes sense if you have an experienced team to run mail infrastructure, if your sending volume is very high and predictable, or if you need custom routing logic.

The two approaches are not mutually exclusive: many teams run their own Postfix server but route external delivery through SmartHost to solve reputation and port problems. A detailed comparison of cost, effort and risk is on SMTP relay or your own SMTP server. For mailboxes that people write from, use email hosting, business email or xMail; SmartHost works alongside them, not instead of them.

What kind of email can you send with SmartHost?

SmartHost is for transactional mail that recipients expect and for informational sends to lists that have given consent; unsolicited bulk email (spam) is strictly not accepted and leads to the account being suspended. Examples of acceptable and unacceptable use:

Commercial email rules apply wherever you send: in Türkiye, for example, businesses must obtain recipients’ consent and comply with the national commercial message register (İYS); other countries have their own consent rules. Review these obligations with your legal adviser before sending campaigns. Adding a working unsubscribe link to every marketing message matters both legally and for deliverability.