# Supported PHP and WordPress versions

Source: https://catalystgroup.gg/docs/email-delivery/supported-php-versions/
Updated: 2026-10-19 · By Duane Garner

CRM-NG SMTP needs PHP 7.4 or newer and WordPress 5.5 or newer. What happens on older versions and how to upgrade safely.

This article lists the PHP and WordPress versions CRM-NG SMTP supports, explains the notices you see on older versions, and shows how to upgrade. It is for site owners whose site shows a version notice, and for anyone checking requirements before installing.

 

## Requirements

 

| Software | Minimum | Recommended |
| --- | --- | --- |
| PHP | 7.4 | A version your host still supports with security updates (8.1 or newer) |
| WordPress | 5.5 | The latest release |

 

The plugin also uses PHP's built-in **libsodium** to encrypt saved passwords. It is part of every standard PHP build from 7.2 onwards, so you rarely need to do anything about it.

 

## How to find your versions

 
1. Open Site Health
  In the WordPress admin, go to **Tools → Site Health** and click the **Info** tab.
2. Read the versions
  Expand **WordPress** for the WordPress version, and **Server** for the PHP version.

 

Your hosting control panel also shows the PHP version, usually on a page called **PHP version**, **PHP settings** or **MultiPHP Manager**.

 

## What happens on an older PHP version

 

If your server runs a PHP version older than 7.4, CRM-NG SMTP does not load at all. This protects your site from errors. You see a red notice in the admin:

 

> **Warning:** Your site is running an insecure version of PHP that is no longer supported. Please contact your web hosting provider to update your PHP version.
>  
> CRM-NG SMTP plugin is disabled on your site until you fix the issue.

 

While the plugin is disabled, WordPress sends email the old way, through your host's PHP mail, so your settings are kept but not used.

 

## What happens on an older WordPress version

 

If WordPress is older than 5.5, you see:

 

> **Warning:** Your site is running an old version of WordPress that is no longer supported by CRM-NG SMTP. Please update your WordPress site to at least version 5.5.
>  
> CRM-NG SMTP plugin is disabled on your site until WordPress is updated to the required version.

 

Again, nothing is deleted. The plugin starts working as soon as you update.

 

## How to upgrade PHP safely

 

Old PHP versions no longer receive security fixes, so upgrading helps far more than this one plugin.

 
1. Back up the site
  Take a full backup of files and database, or ask your host to.
2. Check your other plugins and theme
  Make sure they are up to date. Outdated plugins are the usual cause of problems after a PHP upgrade.
3. Try it on staging first
  If your host offers a staging copy, switch PHP there and click through the site.
4. Switch the PHP version
  In your hosting control panel, choose the new version, or ask your host's support to do it.
5. Check the site
  Visit the front end and the admin. Then send a test from **CRM-NG SMTP → Tools → Email Test**.

 

If something breaks, most control panels let you switch back to the previous PHP version straight away.

 

## How to update WordPress

 

Go to **Dashboard → Updates** and click **Update to version …**. Take a backup first. If your host manages WordPress updates for you, ask them.

 

## A known issue on some PHP 7.4 servers

 

Some servers run PHP 7.4 with an old copy of the **libpcre2** library (version 10.32 or earlier). On those servers, valid email addresses can be rejected as invalid. If this happens, the failed-send banner says that your server *"is running PHP 7.4.x with an outdated libpcre2 library"*. Ask your host to update the library, or move to a newer PHP version, which fixes it.

 

## Related

 
- [Installing and activating CRM-NG SMTP Email](https://catalystgroup.gg/docs/email-delivery/install-and-activate/)
- [Site Health checks](https://catalystgroup.gg/docs/email-delivery/site-health-checks/)
- [Updates and the changelog](https://catalystgroup.gg/docs/email-delivery/changelog-and-updates/)
- [Troubleshooting email delivery](https://catalystgroup.gg/docs/email-delivery/troubleshooting/)