Cause
Various
Resolution
Make sure you have an active Internet connection by checking to see if you can access websites. Next, try restarting your device, and afterwards check your TechMail account's configuration in the Mail app.
NOTE: Android is highly customizable and may look different depending on your manufacturer. The steps below may vary for different devices.
1) Open your default web browser and make sure that you have an established Internet connection by browsing to several websites. Try both TTU and non-TTU websites (i.e., https://www.ttu.edu and https://www.google.com). If your Internet connection is not active, you will not be able to send email messages using the Mail client. Resolve the Internet connection problem first, and then proceed with these steps if needed.
2) Try powering down your device and then turning it back on.
3) Once you are certain that your Internet connection is working successfully, go to your Email app and ensure that the Mail settings are correct for your TechMail account.
3a) Open the Email app.
3b) Tap the menu button (hamburger icon).
3c) Tap the settings cog (gear icon).
3d) Tap your account.
3e) Scroll down and tap Exchange server settings.
3f) Correct any information that you need to update, and then tap Done.
OUTCOME
You are able to send and receive TechMail from your Android device.
Workaround
You may access TechMail through Outlook on the web using your default web browser.