You can send an email without open tracking. Mailsuite won't add the tracking pixel, so you won't see when that email is opened.
This only turns off open tracking. The email is still sent through Mailsuite, and any tracked links or documents you've added to it are still tracked.
To turn off open tracking for one email:
1) In the Gmail compose window, click the Mailsuite button next to Send.
2) Uncheck Track email opens.
3) Send the email.
To turn off open tracking for all your emails, see Disable Mailtrack email tracking by default.