No. The only ways to message attendees through the system are either through the meeting reminder/welcome system emails or adding yourself as an attendee and using the direct messaging function. This is because we have found it is a lot ore likely that an attendee will respond to an email if it comes directly from the event manager.
Otherwise, personalised emails must be sent through a third party email client or by customising the system emails, sending the email and reverting said system email back to its original state. In this situation, using an email client outside the system would be a lot easier and take up less time.
Learn how to customise system emails by visiting this article.