Internationalization improvements in 6.8

Various internationalization (i18n) improvements are in WordPress 6.8, and this developers note focuses on these.

Localized PHPMailer messages

Over 12 years after #23311 was reported, WordPress 6.8 now properly localizes any user-visible PHPMailer error messages. To achieve this, a new WP_PHPMailer class extending PHPMailer was introduced to leverage the WordPress i18n system with PHPMailer. Note that developers don’t typically interact with this class directly outside of wp_mail() or the phpmailer_init action.

See [59592] for more context.

Plugin update emails in the admin’s locale

This was reported and fixed in #62496. It’s a follow-up to the email localization change introduced in