By removing the call to apply_filters in your plugged wp_mail() override you are introducing a breaking change that causes other plug-ins to stop functioning as intended.
Not sure if this was intended to resolve the documented issue with the "$to" variable, but one unintended side-effect is that it also no longer filters any other message data as well, including headers, subject, and message body.
I've confirmed that the "Email Templates" plug-in ceases to function when "Mailgun" is active. Deactivating the plug-in resolves all underlying e-mail formatting issues.
By removing the call to
apply_filters
in your plugged wp_mail() override you are introducing a breaking change that causes other plug-ins to stop functioning as intended.Not sure if this was intended to resolve the documented issue with the "$to" variable, but one unintended side-effect is that it also no longer filters any other message data as well, including headers, subject, and message body.
I've confirmed that the "Email Templates" plug-in ceases to function when "Mailgun" is active. Deactivating the plug-in resolves all underlying e-mail formatting issues.