Send a one off email to a list member after email address update

Here is the scenario. We send out a mass email with how-to instructions for new features of our website. One of our members call because they cannot access it because they never received the how-to email. Their email hasn't been updated in our lists so I manually update it and just want to resend that how-to email to just them at their newly updated email address and not to the whole list again. Is there a way to do this? I found a work around by adding them to a test email so they could get those instructions but they called again to ask why it said test at the bottom. So I would like to figure out the proper way to do this if possible.

TIA