WP Mail SMTP plugin causes PHP Fatal Error Memory Exhuasted

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[22-Sep-2022 15:08:07 UTC] PHP Fatal error:  Allowed memory size of 268435456 bytes exhausted (tried to allocate 20480 bytes) in /var/www/html/wordpress/wp-includes/wp-db.php on line 2864
[22-Sep-2022 15:08:07 UTC] PHP Fatal error:  Allowed memory size of 268435456 bytes exhausted (tried to allocate 69632 bytes) in /var/www/html/wordpress/wp-includes/functions.php on line 5275

I am getting the above error when I activate the WP Mail SMTP plugin.

I have more than enough memory allocated in both the wp-config.php file and the php.ini file.

Every other plugin on the site works, except this one.