# Encoding

Text and HTML message bodies are encoded with the quotedprintable mechanism by default. Message headers are also encoded with the quotedprintable mechanism if you do not specify base64 in `setHeaderEncoding()`. All other attachments are encoded via base64 if no other encoding is given in the `addAttachment()` call or assigned to the MIME part object later. 7Bit and 8Bit encoding currently only pass on the binary content data.

Header Encoding, especially the encoding of the subject, is a tricky topic. `Zend_Mime` currently implements its own algorithm to encode quoted printable headers according to RFC-2045. This due to the problems of `iconv_mime_encode` and `mb_encode_mimeheader` with regards to certain charsets. This algorithm only breaks the header at spaces, which might lead to headers that far exceed the suggested length of 76 chars. For this cases it is suggested to switch to BASE64 header encoding as the following example describes:

    // By default Zend_Mime::ENCODING_QUOTEDPRINTABLE
    $mail = new Zend_Mail('UTF-8');

    // Reset to Base64 Encoding.
    $mail->setHeaderEncoding(Zend_Mime::ENCODING_BASE64);

`Zend_Mail_Transport_Smtp` encodes lines starting with one dot or two dots so that the mail does not violate the SMTP protocol.