{"id":57122,"date":"2022-10-25T03:01:35","date_gmt":"2022-10-24T17:01:35","guid":{"rendered":"http:\/\/www.rjmprogramming.com.au\/ITblog\/?p=57122"},"modified":"2022-10-25T05:56:53","modified_gmt":"2022-10-24T19:56:53","slug":"php-inline-html-gmail-duplicate-header-field-troubleshooting-tutorial","status":"publish","type":"post","link":"https:\/\/www.rjmprogramming.com.au\/ITblog\/php-inline-html-gmail-duplicate-header-field-troubleshooting-tutorial\/","title":{"rendered":"PHP Inline HTML Gmail Duplicate Header Field Troubleshooting Tutorial"},"content":{"rendered":"
\"PHP<\/a>

PHP Inline HTML Gmail Duplicate Header Field Troubleshooting Tutorial<\/p><\/div>\n

Yesterday’s Exim Mail Server Troubleshooting Primer Tutorial<\/a> represented a mail server level of issue with emailing hereabouts.<\/p>\n

Another level of issue with emailing can occur with our inhouse PHP created inline HTML emails to Gmail<\/a>, where we’ve again used Exim<\/a>‘s exim_mainlog log file to discover …<\/p>\n

<\/img><\/p>\n

… whereby we’d been, in the headers of the PHP mail<\/a> email message, specifying the “To:” field twice, and at the Gmail end, this email is blocked until we modified PHP as per<\/font> …<\/p>\n

<?php
\n
\n if ($message != \"\") { \/\/ inline HTML
\n
\n \/\/ To send HTML mail, the Content-type header must be set
\n $hdrs[] = 'MIME-Version: 1.0';
\n if ($subd != \"\") {
\n $hdrs[] = 'Content-type: application\/pdf';
\n } else {
\n $hdrs[] = 'Content-type: text\/html; charset=iso-8859-1';
\n }
\n
\n \/\/ Additional headers
\n if (strpos(strtolower($to), \"@gmail.com\") === false) { <\/font>\/\/!in_array('To: ' . $to, $hdrs)) {
\n $hdrs[] = 'To: ' . $to;
\n }<\/font>
\n $hdrs[] = 'From: ' . $fromer;
\n
\n if ($cc != \"\") { $hdrs[] = 'CC: ' . $cc; }
\n if ($bcc != \"\") { $hdrs[] = 'BCC: ' . $bcc; }
\n $hdrs[] = 'Reply-To: ' . $fromer;
\n
\n \/\/ Mail it
\n $fflist=\"inline HTML\";
\n zmail($to, $subject, $message, implode(\"\\r\\n\", $hdrs));
\n } else {
\n zmail($to, $subject, \"\", $headers);
\n }
\n<\/code>
\n?><\/p>\n

… in the changed inhouse PHP email helper<\/a> emailhtml.php<\/a> to remedy this situation<\/a>.<\/p>\n

Did you know?<\/i><\/b><\/p>\n

Though the exim_mainlog panned out to be telling the truth, we wanted to see the issue for ourselves. Fortuitously, yesterday’s allowed through inline HTML email example<\/a> was also an example of leniency at Gmail<\/a> (as well as engendering a false sense of security)<\/font> to allow through and we were able to reference that email’s vertical “ …<\/span>” menu’s “Show original” suboption to see the duplicate ‘To:’ header fields<\/a> that would later cause another blockage. The “Show original” suboption here can be very useful.<\/p>\n

And on macOS or Linux command line, in dynamic logging situations, the (in our case) …<\/p>\n


\n# tail -f \/var\/log\/exim_mainlog
\n<\/code><\/p>\n

… followed by the sending of an inhouse PHP mail created inline HTML email, and then after a bit, control-C back at the tail operation, was a good way to investigate a little subset of relevant logging activity, via the macOS Terminal application scrolling (up) abilities.<\/p>\n

\n

\n

Previous relevant Exim Mail Server Troubleshooting Primer Tutorial<\/a> is shown below.<\/p>\n

\"Exim<\/a>

Exim Mail Server Troubleshooting Primer Tutorial<\/p><\/div>\n

Exim Internet Mailer<\/a>, as our Mail Server software here at this RJM Programming web server, has seemed an enigma, especially when, a while back (tut, tut)<\/font> it went quite quiet sending out emails to Gmail<\/a> recipients, at the very least. Take a look at the directory structure of exim, and you might join me!<\/p>\n

However, today, we stepped back and got past our vague “spam” theories, and got inspiration from the excellent advice at send a testmail via exim – makandra Operations<\/a>, thanks, to try, at our RJM Programming ssh access terminal command line session, typing …<\/p>\n


\n# exim -v rmetcalfe15@gmail.com
\nFrom: user@domain.name
\nSubject: Foobar
\nText Text Text
\n
\nI like Pie!
\n<control-D><\/font>
\n<\/code><\/p>\n

… ended by (macOS keyboard) control-D to get to see the exim error logging dynamically. Was it the monochrome<\/font> colour and scrolling<\/font> movement that finally got me to take my head out of the sand?!<\/p>\n

The logging that followed reasoned …<\/p>\n

\n SMTP error from remote mail server after end of data: host gmail-smtp-in.l.google.com: 421-4.7.0 This message does not pass authentication checks (SPF and DKIM both do\\n421-4.7.0 not pass). SPF check does not pass\\n421-4.7.0 with ip.To best protect our users from spam, the\\n421-4.7.0 message has been blocked. Please visit\\n421-4.7.0 https:\/\/support.google.com\/mail\/answer\/81126#authentication for more\\n421 4.7.0 information.\n<\/p><\/blockquote>\n

… and gave me a link to follow up with at Prevent mail to Gmail users from being blocked or sent to spam – Gmail Help<\/a>, thanks, which honed my attention to possible need for, first off …<\/p>\n