public function setSystemMessageType($messageType): Envelope
    {
        if (!in_array($messageType, static::getLetterTypeOptions())) {
            throw new InvalidArgumentException(
                sprintf('Property %s is not supported for %s', $messageType, __FUNCTION__)
            );
        }

        $this->data['letterType']['systemMessageType'] = $messageType;

        return $this;
    }
public function setSystemMessageType($messageType): Envelope
    {
        if (!in_array($messageType, static::getLetterTypeOptions())) {
            throw new InvalidArgumentException(
                sprintf('Property %s is not supported for %s', $messageType, __FUNCTION__)
            );
        }

        $this->data['letterType']['systemMessageType'] = $messageType;

        return $this;
    }
public function setSystemMessageType ( $ messageType ) : Envelope { if ( ! in_array ( $ messageType , static :: getLetterTypeOptions ( ) ) ) { throw new InvalidArgumentException ( sprintf ( 'Property %s is not supported for %s' , $ messageType , __FUNCTION__ ) ) ; } $ this -> data [ 'letterType' ] [ 'systemMessageType' ] = $ messageType ; return $ this ; }
Specify the type of E-POST letter

@param string $messageType

@return self
@throws InvalidArgumentException
Specify the type of E - POST letter