1 month Limit? Can you reference where it indicates that? I only get 1 week!
Assuming you are using the stock Email app for Android, use these steps:
First, open the app > see the 3 dots in the top right corner? tap that > tap Settings > tap Manage Accounts > tap your email address > tap Sync settings > tap Period to sync Email > select desired range (example: "All" to see every email)
Now you've changed your settings, arrow back until you reach your inbox. If you still don't see your emails, tap the circular refresh arrow.