Publication is necessary for defamation. Publication must be intentional or negligent. Here publication does not mean giving the publicity but to make the statement known to other person than the person defamed.
If a defendant has committed defamatory statement only to the plaintiff and to none else then it shall not amount to defamation. If he of his own will hands it over to someone else who reads it, it will be publication by himself and, therefore defendant cannot be responsible, but where he is under a duty to send it to some other person, defendant is liable.
In Pullman v. Hill, [(1891) 1 OS 524, the plaintiff dropped a letter in an open card containing defamatory matter, which is likely to be read by somebody else. It was held that it amounts to publication.
In Theaker v. Richardson, [(1962) 1 All ER 229] it was held that to send something via telegram or postcard that could be read by others can be claimed as publication.
In Delacroix v. Thevenot, [(1817) 2 Stark 63], ii was observed that if a person knowingly sends something in writing to defame a person in a closed envelope that it will be opened by someone else, then this amounts to publication.
In Sadgrove v. Hole, [(1829) 10 BRC 263] the defendant sent to a third person a post card containing a defamatory statement relating to the plaintiff, but plaintiff’s name was not mentioned, and no stranger unacquainted with the circumstances would have known to whom it referred.