Gmail SMTP Mailer

[tilmanharms]

Thanks @Brandin and @mudmin for the fast and detailed responses! I will go through them in detail tomorrow. In the meantime I have managed to "correct" the missing message-ID value by replacing less and greater than signs in the sprintf formatting string in 'users/vendor/phpmailer/phpmailer/src/PHPMailer.php':

Code:

2288             //$this->lastMessageID = sprintf('<{3bc1fe685386cc4c3ab89a3f76566d8931e181ad17f08aed9ad73b30bf28114d}s@{3bc1fe685386cc4c3ab89a3f76566d8931e181ad17f08aed9ad73b30bf28114d}s>', $this->uniqueid, $this->serverHostname());

Code:

2289             $this->lastMessageID = sprintf('<{3bc1fe685386cc4c3ab89a3f76566d8931e181ad17f08aed9ad73b30bf28114d}s@{3bc1fe685386cc4c3ab89a3f76566d8931e181ad17f08aed9ad73b30bf28114d}s>', $this->uniqueid, $this->serverHostname());

I'm not sure why php sprintf() does this on the RedHat server (PHP 5.6.27) and not on the SiteGround account (PHP 7.0.27), if it's the version or a setting... Unfortunately this hasn't yet fixed the fact that emails are not arriving at my gmail account.