WordPress with WP Mail SMTP

Send your WordPress site's emails through Mailcheer: set up the WP Mail SMTP "Other SMTP" mailer, keep your key in wp-config.php, send a test email.

WordPress sends its own emails: form notifications, password resets, messages from your plugins. The WP Mail SMTP plugin routes them through the SMTP server of your choice, in this case Mailcheer's. No code required.

Before you start

• A verified domain in Mailcheer. Your site's sender address must belong to it. To verify a domain, follow Verify your domain.
• Your SMTP credentials. In Mailcheer, open Integrations → From your website or software and click Create my credentials. The key is shown only once, so copy it right away.
• The WP Mail SMTP plugin, installed and activated on your site.

The values you will need:

Set up WP Mail SMTP

1. In the WordPress menu, go to WP Mail SMTP → Settings and open the General tab.
2. In From Email, enter an address on your verified domain, such as hello@your-domain.com.
3. Check Force From Email. The WP Mail SMTP documentation recommends it: the address then applies to emails from every plugin on your site.
4. In From Name, enter the name your recipients will see. It defaults to your site's name.
5. Under Mailer, select Other SMTP. A new settings section appears.
6. In SMTP Host, enter smtp.mailcheer.com.
7. Under Encryption, choose TLS.
8. In SMTP Port, enter 587.
9. Turn Authentication on.
10. In SMTP Username, enter mailcheer.
11. In SMTP Password, paste your Mailcheer key.
12. Click Save Settings at the bottom of the page.

Prefer port 465? Choose SSL under Encryption and enter 465 in SMTP Port. Everything else stays the same.

Safer: keep the key in wp-config.php

The WP Mail SMTP documentation recommends putting your SMTP username and password in your site's configuration file, wp-config.php, instead of the admin area. In the admin area, any administrator on the site can see and edit them, and they are stored in your database.

Open wp-config.php, find the line /* That's all, stop editing! Happy publishing. */ and paste these three lines just above it:

define( 'WPMS_ON', true );
define( 'WPMS_SMTP_USER', 'mailcheer' );
define( 'WPMS_SMTP_PASS', '<your Mailcheer key>' );

Save the file. In WP Mail SMTP → Settings, the fields set this way are grayed out and can no longer be edited, which tells you the constants are working.

Test it

1. Go to WP Mail SMTP → Tools and open the Email Test tab.
2. In Send To, enter an address whose inbox you can check.
3. Leave the HTML setting on, as the WP Mail SMTP documentation recommends.
4. Click Send Email. A success message appears: check that the email arrived.

If your site has forms that send emails, submit a test entry or two as well. The WP Mail SMTP documentation suggests it, so you know those emails use the same settings.

Then go back to Mailcheer, to Integrations → From your website or software. As soon as the first email arrives, the page shows that the connection works: Connected. It also lists recent rejections, with the reason for each.

Troubleshooting

• You see "SMTP Error: Could not authenticate". Check that the username is exactly mailcheer, then paste the key again in full, with no space before or after it. If you use constants, make sure they sit above the line /* That's all, stop editing! Happy publishing. */.
• You see "Could not connect to SMTP host". The WP Mail SMTP documentation names incorrect SMTP settings as the most common cause. Check the host, smtp.mailcheer.com, then the port and encryption pair: 587 with TLS, or 465 with SSL. Port and encryption go together, so don't mix the two pairs.
• The email is rejected. Read the reason shown in Mailcheer under Integrations → From your website or software. The sender address must belong to a verified domain: check From Email and keep Force From Email checked, so no plugin sends from another address.

Sources

• Other SMTP Mailer — WP Mail SMTP — accessed September 25, 2026
• Securing SMTP Settings With Constants — WP Mail SMTP — accessed September 25, 2026