The Custom SMTP provider sends your campaigns through any SMTP server (SMTP is the standard protocol for sending email): your host’s mail server, your company mailbox, or an email service’s SMTP relay. It is included in MailerPress (free), delivers much better than PHP Mail, and supports bounce tracking through an IMAP mailbox.
Get your SMTP settings
Ask your host or email provider for:
- the SMTP server name or IP address (e.g.
smtp.example.com); - the port and the encryption type, which secures the connection (usually 587 with TLS, or 465 with SSL);
- the username and password of the SMTP account;
- the sender addresses this account may use.
Connect your SMTP server
- Go to MailerPress > Integrations, on the Email Service Providers tab.
- On the Custom SMTP card, click Configure.
- Fill in the fields described below, then click Save changes.
- On the Custom SMTP card, now under Configured Providers, turn on the Enable toggle.
- Click Set as primary provider to send your emails with this server.
| Field | What to enter |
|---|---|
| SMTP Host Name | The URL (e.g. smtp.mailprovider.com) or IP address of your SMTP server. |
| SMTP port | The port given by your provider: typically 465 with SSL, 25 or 587 with TLS. Empty by default: fill it in. |
| Auto TLS | Off by default. See the next section. |
| Encryption | TLS (default), SSL or None. |
| Authentication | Turn it on if your server requires a username and password (almost all do). Off when you first open the settings. |
| Authentication ID | The SMTP username, often your full email address. Shown when Authentication is on. |
| Authentication password | The SMTP password (or app password). Shown when Authentication is on. |
| Default sender email address | The default From address. Use an address your SMTP account may send from. |
| Default sender name | The default From name. |
Choose the encryption
- TLS (usually port 587): the connection starts unencrypted, then switches to TLS (STARTTLS). With Auto TLS off, MailerPress requires TLS and sending fails if the server doesn’t offer it. With Auto TLS on, MailerPress uses TLS when the server offers it. Turn Auto TLS on only if a strict TLS connection fails with your server.
- SSL (usually port 465): the connection is encrypted from the start.
- None: no encryption. Use it only with a local test server (MailHog, Mailpit…). If you also turn off Authentication, MailerPress connects without a username and password.
Send a test email
- On the Custom SMTP card, open the three-dot Actions menu and click Send test email.
- Enter a recipient in Send to and click Send.
You should receive an email with the subject “This is a Sending Method Test”. If the test fails, MailerPress shows the reason:
- Connection refused or Connection timed out: check the host name and port, and ask your host whether your server may open outgoing SMTP connections.
- Authentication failed: check the Authentication ID and password. Some providers require an app password instead of your usual password.
- SSL/TLS connection error: the encryption doesn’t match the port. Try TLS with port 587 or SSL with port 465, or turn on Auto TLS.
- SMTP authentication credentials are required: Authentication is on but the ID or password is empty.
Set the sending speed
Go to MailerPress > Settings > Sending frequency (or click Adjust sending frequency on the card) and pick a profile that fits your SMTP server’s limits:
| Profile | Settings | Emails per hour |
|---|---|---|
| Conservative (Gmail SMTP, free providers) | 25 emails every 5 minutes, 3 emails/second | 300 |
| Balanced (Recommended – Most SMTP servers) | 50 emails every 5 minutes, 8 emails/second | 600 |
| Performance (Dedicated SMTP servers) | 100 emails every 3 minutes, 15 emails/second | 2,000 |
Many hosts and mailbox providers cap the number of emails per hour or per day. Choose a profile below that cap, or set your own values in Manual mode. See How to change your sending frequency in MailerPress.
Enable bounce tracking (IMAP)
A bounce is an email returned as undeliverable (for example, the address doesn’t exist). With Custom SMTP, MailerPress detects bounces by reading a mailbox that receives them, over IMAP (the protocol for reading a mailbox). Create a dedicated mailbox (e.g. [email protected]), then:
- Open the Custom SMTP settings and turn on Enable bounce tracking (IMAP).
- Fill in Bounce Receiver Email Address (the address that receives bounces), IMAP Host (e.g.
mail.example.com), IMAP Port (993 – IMAP over SSL/TLS (recommended), 143 – IMAP without encryption, or Other (enter manually)), Username (the mailbox’s full email address) and Password. - Keep Validate SSL Certificate on, unless your mail server uses a self-signed certificate.
- Click Test & Save Bounce Config. MailerPress connects to the mailbox and saves the settings only if the connection works (IMAP connection successful).
Once saved, MailerPress uses the bounce address as the return path (or envelope sender: the hidden address where servers send bounce messages) of emails sent through your SMTP server. Every 12 hours, MailerPress reads the unread messages in the mailbox inbox, marks the matching contacts as bounced and marks the messages as read. Use a mailbox that receives nothing else. If your SMTP provider replaces the return path with its own address, bounces don’t reach your mailbox and can’t be detected this way.
Turning off Enable bounce tracking (IMAP) deletes the saved mailbox settings.
To see bounced contacts, go to MailerPress > Audience > All Contacts and click the Bounced tab. They no longer receive your campaigns.
Reply-to address
Custom SMTP supports a reply-to address. Set Reply-to email and Reply-to name in MailerPress > Settings > General, section Email senders. If they are empty, replies go to the From address. See Customize the default sender name and email address.
To compare Custom SMTP with the other sending services, see Choose and configure your email sending service.