新行（ ）在电子邮件正文中不起作用

I am using PHP mail() function:

    $to      = 'AAAA <postmaster@xxx.xx>';
    $subject = 'BBBB';
    $message = "CCCC
CCCC CCCC  CCC 
 CCC 
 CCC 
 CCCC";
    $headers = 'From: DDD<postmaster@xxx.xx>' . "
";
    $headers .= "Content-Type: text/html; charset=\"UTF-8\"; format=flowed 
";
    $headers .= "Mime-Version: 1.0 
"; 
    $headers .= "Content-Transfer-Encoding: quoted-printable 
";
    mail($to, $subject, $message, $headers);

When I receive this email it looks like this:

CCCC CCCC CCCC CCC CCC CCC CCCC

I would expect something like this:

CCCC
CCCC CCCC CCC 
CCC 
CCC 
CCCC

It works fine without Content-Type HTTP header. How can I make new lines and still use my "Content-Type" declaration?

You need to use a <br> because your Content-Type is text/html.

It works without the Content-Type header because then your e-mail will be interpreted as plain text. If you really want to use you should use Content-Type: text/plain but then you'll lose any markup.

Also check out similar question here.

You need to use <br> instead of . For this you can use built in function call nl2br So your code should be like this

 $message = nl2br("CCCC
CCCC CCCC  CCC 
 CCC 
 CCC 
 CCCC");

If you are sending HTML email then use <BR> (or <BR />, or </BR>) as stated.
If you are sending a plain text email then use %0D%0A
= %0D (Ctrl+M = carriage return)
= %0A (Ctrl+A = line feed)

If you have an email link in your email,
EG

<A HREF="mailto?To=...&Body=Line 1%250D%250ALine 2">Send email</A>

Then use %250D%250A

%25 = %

If you use content-type: text/html you need to put a <br> because your message will be threated like an html file.

But if you change your content-type to text/plain instead of text/html you will be able to use characters.

Using <BR> is not allways enough. MS Outlook 2007 will ignore this if you dont tell outlook that it is a selfclosing html tag by using

 <BR />

This worked for me.

$message  = nl2br("
===============================

www.domain.com 

===============================

From: ".$from."

To: ".$to."

Subject: ".$subject."

Message: ".$_POST['form-message']);

You can add new line character in text/plain content type using %0A character code.

For example:

<a href="mailto:someone@example.com?subject=Hello%20again&body=HI%20%0AThis%20is%20a%20new%20line"/>

Here is the jsfiddle

' '   

space was missing in my case, when a blank space added ' ' started to work

Another thing use "", there is a difference between " " and ' '.

" " produces 2 new lines while " ","" & " " produce single lines if, in the Header, you use content-type: text/plain.

Beware: If you do the Following php code:

    $message='ab<br>cd<br>e<br>f';
print $message.'<br><br>';
    $message=str_replace('<br>',"
",$message);
print $message;

you get the following in the Windows browser:

ab
cd
e
f

ab cd e f

and with content-type: text/plain you get the following in an email output;

ab
cd
e
f

for text/plain text mail in a mail function definitely use PHP_EOL constant, you can combine it with
too for text/html text:

$messagePLAINTEXT="This is my message."
. PHP_EOL .
"This is a new line in plain text";

$messageHTML="This is my message."
. PHP_EOL . "<br/>" .
"This is a new line in html text, check line break in code view";

$messageHTML="This is my message."
. "<br/>" .
"This is a new line in html text, no line break in code view";