Hi DonMcAuley,
If you are referring to the default text size of your instant messages when sending it using Messenger client. You can change it by following these steps:
- Open Messenger client and sign in using your account.
- On the program window open a chat window to any of your contacts that are available.
- Once you have opened a conversation window to one of your contacts, please click the Tools option found on the action bar of the conversation window beside Help option *(In case the action bar is hidden, just simply press the ALT key on your keyboard to unhide it.),*and click the Text size.. option to customize your current text font.
- After customizing it, click OK button to save the changes.
Let us know the result afterwards.
Thank you.