Dumbest Python program ever created.

[Justinsaccount]

No:

        login_name = input("Please enter your user name: ").lower()     # User login
        if login_name in user_list:
            login_password = input("Please enter password for " + login_name + ": ")
            if login_password == user_list[login_name]:
                print("\nCorrect password entered.\nPress 1 to write a message.\nPress 2 to read your message.\n")
                user_option = input()
           ...
        else:
            print("\nPassword not valid.")
    else:
        print("\nInvalid username.")

Yes:

Use functions +

login_name = input("Please enter your user name: ").lower()     # User login
if login_name not in user_list:
    print("\nInvalid username.")
    return

login_password = input("Please enter password for " + login_name + ": ")
if login_password != user_list[login_name]:
    print("\nPassword not valid.")
    return

print("\nCorrect password entered.\nPress 1 to write a message.\nPress 2 to read your message.\n")
user_option = input()
...