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How to Send WordPress Email Through BillionMail SMTP (WP Mail SMTP Setup)

WordPress sends email with PHP's

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mail()

function by default. On most VPS servers that mail either doesn't go out at all or lands in spam, because it isn't signed and doesn't come from a real mailbox. Contact form messages, WooCommerce order emails and password resets quietly disappear.

If you run BillionMail, the fix is easy: let WordPress log in to a real BillionMail mailbox over SMTP. The mail is then signed with your domain's DKIM key and sent by a server your SPF record trusts.

Step 1: Create a mailbox for the site
In BillionMail, open Mailboxes and click Add Mailbox. Create something like

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[email protected]

or

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[email protected]

with a long, random password. A separate mailbox per site means you can change one password without breaking other sites. More on this in BillionMail mailboxes and webmail.

Every mailbox is listed under Mailboxes. The Copy button in the Login Info column copies the server addresses and ports you need:


The copied text looks like this:

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WebMail: https://mail.example.com/roundcube Username: [email protected] Password: ... IMAP service [ Address: mail.example.com Port: 143/993 ] SMTP service [ Address: mail.example.com Port: 25/465/587 ]

The SMTP service address is what WordPress needs.

Step 2: Install WP Mail SMTP
In WordPress go to Plugins > Add New, search for WP Mail SMTP, install and activate it. The free version is enough. (FluentSMTP or Post SMTP work the same way if you prefer them.)

Step 3: Enter the SMTP settings
Open WP Mail SMTP > Settings and set:

• From Email: the mailbox you created, for example
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  [email protected]
  . Tick Force From Email so plugins can't change it to an address your server isn't allowed to send for.
  
• From Name: your site name.
  
• Mailer: Other SMTP.
  
• SMTP Host:
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  mail.example.com
  (the address from the Login Info).
  
• Encryption: TLS with port 587, or SSL with port 465. Both are fine; don't use port 25 for this.
  
• Authentication: on. Username is the full email address, password is the mailbox password.
  

Save, then open the Tools > Email Test tab and send a test to a Gmail address.

Keep the password out of the database (optional)
WP Mail SMTP can read the password from

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wp-config.php

instead of storing it in the database:

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define( 'WPMS_ON', true ); define( 'WPMS_SMTP_PASS', 'your-mailbox-password' );

Put these lines above

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/* That's all, stop editing! */

.

WordPress on the same server as BillionMail?
That works too. Still use the hostname

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mail.example.com

, not

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localhost

, or the certificate won't match and the TLS connection fails. If the server can't reach its own public IP, add a line to

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/etc/hosts

on the server pointing

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mail.example.com

to the server's IP.

If the test fails

• "Could not connect" or a timeout: port 587 or 465 is closed in your firewall or the provider's cloud firewall. Test from the WordPress server:
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  nc -vz mail.example.com 587
  .
  
• "Authentication failed": wrong password, or the username isn't the full address. Try logging in to webmail with the same details.
  
• Certificate errors: the mail hostname has no valid certificate. See BillionMail SSL certificate won't apply.
  
• Test arrives, but in spam: see emails going to spam even though SPF, DKIM and DMARC pass.
  

Once it works, submit your contact form once and reset a test user's password to be sure every type of email goes out. If your app isn't WordPress, the same SMTP details work in Laravel, Django, Ghost or any other app; for code-only sending, the BillionMail Send API is another option.

More BillionMail guides

• Send API for transactional email
  
• Import contacts, groups and tags
  
• Email templates explained
  
• SMTP relay with Amazon SES, Brevo or Mailgun
  
• Mailboxes and webmail
  
• Campaign analytics explained
  
• IP warm-up plan
  
• Move from Mailchimp or Sendy
  
• Add a second sending domain
  
• Send your first newsletter · DNS setup explained · Deliverability testing
  

Applies to BillionMail 4.9, October 2026. Replace

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example.com

and

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mail.example.com

with your own domain and mail hostname. Menu names can change a little between versions.