I have seen that upgrading PHP version to 8.1 gives some problems if you have wordpress debug enabled:
You can see it here: https://plugintests.com/plugins/wporg/mail-mint/latest
Basically I get this error: Deprecated: Constant FILTER_SANITIZE_STRING is deprecated in /var/www/vhosts/yourwebsite.com/sub.yourwebsite.com/wp-content/plugins/mail-mint/app/MrmCommon.php on line 187 (184 to 187)
I guess you are aware of this error, is there any quick solution?
My WordPress is all up to date and up to date.
Thank you very much!