jodd-mail/src/main/java/jodd/mail/EmailFilter.java
public EmailFilter header(final String headerName, final String pattern) {
		final SearchTerm term = new HeaderTerm(headerName, pattern);
		concat(term);
		return this;
	}
public EmailFilter header(final String headerName, final String pattern) {
		final SearchTerm term = new HeaderTerm(headerName, pattern);
		concat(term);
		return this;
	}
Defines filter for {@link Header}.

@param headerName The name of the {@link Header}.
@param pattern    String pattern to use for headerName.
@return this