Hi georgedelp,
Thanks for posting in Apple Support Communities.
With your mail not showing the full message, start off with some basics such as force closing mail, restarting iPhone, and making sure you have the latest update installed.
To see if this is an issue with your network, try connecting to a different Wi-Fi network or connect to your cellular network. Make sure that you have the recommended settings in place if this occurs when connected to a specific Wi-Fi network.
Recommended settings for Wi-Fi routers and access points
If this occurs with all networks and multiple email accounts, back up your iPhone to iCloud or your computer and reset the network settings.
Resetting the network settings removes saved VPN, APN, and Wi-Fi network details, including passwords.
To reset, choose: Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings. Your iPhone will be restarted and you can try checking mail again.
Contact Apple Support for additional support.
Regards.