php – 发送电子邮件时是否需要换行？

我正在使用Zend_Mail发送电子邮件.很少有文章(如 this page的第一个例子)建议在邮件正文中包含长行.

问题：

>如果任何一行大于70个字符,是否有必要使用wordwrap()？
>这个“70”人物来自哪里？

RFC 2822和 5322有一个名为Line Length Limits(2.1.1)的部分：

There are two limits that this specification places on the number of
characters in a line. Each line of characters MUST be no more than
998 characters,and SHOULD be no more than 78 characters,excluding
the CRLF.

…

The more conservative 78 character recommendation is to accommodate
the many implementations of user interfaces that display these
messages which may truncate,or disastrously wrap,the display of
more than 78 characters per line,in spite of the fact that such
implementations are non-conformant to the intent of this
specification

听起来像真正的限制是998个字符,78是你真正不需要打扰的东西.