# Testing for plugin and theme conflicts

Source: https://catalystgroup.gg/docs/email-delivery/plugin-and-theme-conflicts/
Updated: 2026-10-19 · By Duane Garner

What the conflict notice means, which kinds of plugins clash with CRM-NG SMTP, and how to find a conflict without breaking your live site.

Sometimes another plugin, or your theme, changes outgoing email in a way that stops CRM-NG SMTP working properly. This article explains the conflict notice, the usual suspects, and a safe way to test. It is for administrators whose test email works but some site emails do not, or who see a conflict notice.

 

## The conflict notice

 

CRM-NG SMTP recognises many other mail and SMTP plugins. When one of them is active, you see a notice like this:

 

> **Note:** Heads up! CRM-NG SMTP has detected *Plugin name* is activated. Please deactivate *Plugin name* to prevent conflicts.

 

The notice has a **Deactivate** button for that plugin. Two plugins that both try to deliver WordPress email fight over each message, so results become unpredictable: some emails go through one, some through the other, and some fail.

 

For a few plugins the notice offers an alternative, such as switching off one setting inside that plugin instead of deactivating it.

 

If the plugin is network-activated on a multisite, deactivate it from **Network Admin → Plugins**.

 

> **Tip:** The mail plugin CRM-NG SMTP was designed to replace, and CRM-NG Marketing's Email Delivery part, are handled differently: CRM-NG SMTP waits in standby instead of showing a conflict. See [Switching from another mail plugin (hand-over)](https://catalystgroup.gg/docs/email-delivery/switching-from-another-mail-plugin/).

 

## Plugins known to conflict

 

The plugin watches for, among others:

 
- **Other SMTP plugins**, such as Easy WP SMTP, Post SMTP, FluentSMTP, Solid Mail and similar "Gmail SMTP" or "SMTP mailer" plugins.
- **Single-provider plugins**, such as the official Mailgun, SparkPost, Postmark and SendGrid plugins, and WP Offload SES.
- **Plugins that block email**, such as Disable Emails.
- **Email designers and suites** that include their own SMTP module, such as the SMTP module in Branda.
- **Shop integrations** that send WooCommerce email through a provider directly, such as Brevo's WooCommerce integration. Turn off its own email sending option, or deactivate it.

 

You only need one mail plugin. If you rely on a feature in one of these, check whether CRM-NG SMTP already offers it.

 

## Plugins that bypass WordPress email

 

Some plugins, such as BuddyPress and Events Manager, can send email through their own system instead of WordPress's standard mail function. Those emails skip CRM-NG SMTP completely: they will not use your mailer and will not appear in the email log. Look in those plugins' settings for an option to use the WordPress default mail, or consult their documentation.

 

## Signs of a conflict without a notice

 
- The test email works, but emails from one plugin never arrive.
- The From address or name is wrong on some emails, even though you set it in CRM-NG SMTP. (Ticking **Force From Email** and **Force From Name** usually fixes this. See [Sender name, address and the Force settings](https://catalystgroup.gg/docs/email-delivery/sender-name-and-address/).)
- Emails appear in the email log with an error that only happens for one plugin's messages.
- Email stopped working right after you installed or updated another plugin or theme.

 

## Test for a conflict safely

 

The classic test is to deactivate everything except CRM-NG SMTP and switch to a default theme. Doing that on a live shop or membership site can break things for visitors, so use one of these safer options.

 

### Option 1: Use a staging copy (best)

 

Most hosts can create a staging copy of your site in a few clicks. Test there, where nobody else is affected.

 

### Option 2: Use a troubleshooting plugin

 

The free **Health Check & Troubleshooting** plugin from the WordPress community adds a troubleshooting mode. It disables plugins and switches the theme **only for your own login session**. Visitors keep seeing the normal site.

 

### The test itself

 
1. Back up first
  Take a backup, even on staging.
2. Leave only CRM-NG SMTP active
  Deactivate all other plugins (or use troubleshooting mode), and switch to a default WordPress theme such as Twenty Twenty-Five.
3. Send a test
  Go to **CRM-NG SMTP → Tools → Email Test** and send one. Then trigger the email that was failing, if its plugin is needed for that (re-enable just that plugin).
4. Re-enable one at a time
  Turn the other plugins back on one by one, testing after each. Switch the theme back last.
5. Spot the culprit
  When the problem returns, the plugin or theme you just enabled is the cause.

 

## When you find the conflict

 
- Check the conflicting plugin's settings for an email or SMTP option and switch it off.
- Update it. Conflicts are often fixed in newer versions.
- Contact its developer with what you found.
- If it duplicates what CRM-NG SMTP does, deactivate it.

 

If the conflict is with a plugin you cannot do without, contact our support with the plugin's name and version. See [Sharing credentials with support safely](https://catalystgroup.gg/docs/email-delivery/sharing-credentials-safely/).

 

## Related

 
- [Troubleshooting email delivery](https://catalystgroup.gg/docs/email-delivery/troubleshooting/)
- [Switching from another mail plugin (hand-over)](https://catalystgroup.gg/docs/email-delivery/switching-from-another-mail-plugin/)
- [Debugging sending issues](https://catalystgroup.gg/docs/email-delivery/debugging-sending-issues/)
- [Using Force From Email](https://catalystgroup.gg/docs/email-delivery/force-from-email/)