I've been using php to send html emails to people daily for over a year and it has always worked until today, all the emails sent to gmail accounts just displayed the html code. I haven't changed any code recently. It always just displays the html code now in gmail instead of showing the hyperlinks and images.
Here's what it shows:
Reply-To: updates@mysite.com
MIME-Version: 1.0
Content-type: text/html; charset=UTF-8
X-Mailer: PHP/5.3.2 Message-Id: <20120426030303.E8B03A295@www1.mysite.com> Date: Wed, 25 Apr 2012 20:03:03 -0700 (PDT)
... etc.
What happened? Did google change something?
This has also started happening for me since yesterday: 25/04/2012. I have been receiving the same email, same format daily for the last few years - and yesterday seized to stop displaying in HTML format!
Comparing the message content - only thing different I can see from a previous email that displayed correctly is the addition after the authentication results of the following:
Date: Wed, 25 Apr 2012 17:31:23 -0700 (PDT) Message-Id: <4f98975b.9cecd80a.7d2a.66b3SMTPIN_ADDED@mx.google.com>
Could this have anything to do with the cause?
Scrap the above - take a look at this stie: http://johndoesdesign.com/blog/2012/php/getting-your-php-html-email-to-render-in-gmail/
It appears the cause is the "\r\n" - use just "\n" instead. Why this would just start happening out of the blue - something must have changed gmail's end. I've tried this and solved the issue for me. Hope it does for you.
I hope this could help u
Send email using the GMail SMTP server from a PHP page
and like Lawrence said, accept your questions so ppl could answer faster and better
来源：https://stackoverflow.com/questions/10327354/how-to-send-html-emails-to-gmail-with-php-yahoo-works-not-gmail