jodd-mail/src/main/java/jodd/mail/SendMailSession.java
private void setHeaders(final Email emailWithData, final MimeMessage msgToSet) throws MessagingException {
		final Map<String, String> headers = emailWithData.headers();
		if (headers != null) {
			for (final Map.Entry<String, String> entry : headers.entrySet()) {
				msgToSet.setHeader(entry.getKey(), entry.getValue());
			}
		}
	}
private void setHeaders(final Email emailWithData, final MimeMessage msgToSet) throws MessagingException {
		final Map<String, String> headers = emailWithData.headers();
		if (headers != null) {
			for (final Map.Entry<String, String> entry : headers.entrySet()) {
				msgToSet.setHeader(entry.getKey(), entry.getValue());
			}
		}
	}
Sets headers in msgToSet with headers from emailWithData.

@param emailWithData {@link Email} with data
@param msgToSet      {@link MimeMessage} to set data into.
@throws MessagingException if there is a failure