wp_mail_charset – Hook | Developer.WordPress.org

Filters the default wp_mail() charset.

Parameters

The default character encoding for wp_mail() is UTF-8. The character encoding can be changed using the wp_mail_charset filter.
While the average user is unlikely to need to change the default character encoding for email, users who need to send email in different languages may find this filter useful.
UTF-8 is still the recommended default character encoding to use since it’s backward compatible with ASCII and can represent nearly all languages. As a result, UTF-8 is the most ubiquitous character encoding being used on the web. Users/developers typically do not need to change the character encoding in order to read/write foreign langauges.
As of Version 3.5, WordPress character encoding is no longer configurable from the Administration Panel and defaults to UTF-8.

$phpmailer->CharSet = apply_filters( 'wp_mail_charset', $charset );

Used by	Description
wp_mail()`wp-includes/pluggable.php`	Sends an email, similar to PHP’s mail function.

Version	Description
2.3.0	Introduced.