WordPress 5.5 upgraded their version of PHPMailer to 6.1.6 from 5.2.27.
I previously worked around a weird PHPMailer bug where if the Reply-To email address was too long, the Reply-To email header would be silently dropped:
This workaround is no longer needed in PHPMailer 6 as PHPMailer now defaults to PHP's internal validate email address routine instead of some custom regex pattern. PHPMailer 6 actually introduces problems when using the previous custom header method, so we'll need to revert a portion of the commits listed above find a new solution to fix this.
WordPress 5.5 upgraded their version of PHPMailer to 6.1.6 from 5.2.27.
I previously worked around a weird PHPMailer bug where if the
Reply-Toemail address was too long, theReply-Toemail header would be silently dropped:This workaround is no longer needed in PHPMailer 6 as PHPMailer now defaults to PHP's internal validate email address routine instead of some custom regex pattern. PHPMailer 6 actually introduces problems when using the previous custom header method, so we'll need torevert a portion of the commits listed abovefind a new solution to fix this.