Safely wrap long HTML lines to avoid Postfix's smtp_line_length_limit

StackOverflow https://stackoverflow.com/questions/17973750

Question

In order to avoid Postfix from wrapping ultra long lines after smtp_line_length_limit (usually 998 characters) I am currently using php's tidy library to wrap long lines in HTML emails (see related question):

$oTidy = new tidy();
$message = $oTidy->repairString($message,
    array("show-errors" => 0, "show-warnings" => false, "force-output" => true, 
    "alt-text" => "Please display images", "bare" => true, "doctype" => "auto", 
    "drop-empty-paras" => false, "fix-bad-comments" => false, "fix-uri" => true, 
    "join-styles" => false, "merge-divs" => true, "merge-spans" => true, 
    "preserve-entities" => true, "wrap" => 68),
    "utf8"
);

Tidy is really good in wrapping long lines with respect to leaving HTML and CSS valid.
Unfortunately it does a lot more like trying to fix invalid HTML markup, changing HTML tags, doctypes, etc.

I only need the line wrapping however - the other stuff tidy does is overhead and sometimes rather annoying than anything else.

Now I have tried to use PHPMailer's wrapText() function. Unfortunately I have found a bug that makes it useless for me.
PHPMailer converts this source code

<html>
    <body>
        Loremipsumdolorsitametconsetetursadipscing<span style="font-family:'Courier New',sans-serif">lorem</span>
    </body>
</html>

to

<html>
    <body>
        Loremipsumdolorsitametconsete<span style="font-family:'Courier
        New',sans-serif">lorem</span>
    </body>
</html>

breaking the font formatting (Courier New) for the word lorem in some clients.

Now my questions:

How can I wrap HTML lines safely without damaging HTML and CSS?

How does Tidy do it? Should I use a DOM parser? Is there a php version of the Tidy source code (I haven't found one)?

Was it helpful?

Solution

The best way to go seems to be quoted-printable encoding as it can break lines into small chunks of characters while preserving readability for content filters without the risk of destroying any formatting.

Base64 would also be an option but would raise the risk of spam classification.

Both options increase the length of the source code however (quoted-printable especially for non-ascii characters).

Side note:
PHPMailer's wrapText() will not be fixed as the described problems can be solved through the mail encoding as described above.

OTHER TIPS

  1. encode your text into base64 using base64_encode()
  2. set appropriate MIME header
  3. split this base64-ed blob into 76 character wide chunks using chunk_split()
  4. Profit!
Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top