Content-Length:

Content-Length:

---

The size of the body of the message

System V Release 4

The Content-Length: header describes the exact size of the body of a message. The size is always a decimal expression of the number of bytes occupied by the body:

 Content-Length: 5678 

It is used by some MUAs to find the end of the message in a large file of many messages. It is always created or added by MUAs or delivery agents and never by MTAs. It should never be declared in the configuration file.