One possibility is updating your mail client software. For example, the Mail app on iPads and iPhones with iOS version 6 or earlier is not secure enough to access Gmail. Update your device’s software to the latest version, which will include an updated Mail app compatible with Gmail security. Another option—which Google does not recommend because it weakens the security of your account—is to change the settings in your Gmail account to allow less secure apps access to it. For some situations, this step may be necessary, so having this option is convenient if a bit risky.
How to Give Less Secure Apps Access to Gmail
Follow these simple steps to set your Gmail account to basic authentication, which allows less secure apps and email clients to connect to your Gmail account through IMAP or POP.
Gmail’s Security
Gmail allows email programs and add-ons to access your messages, labels, and contacts securely by using OAuth. This method ensures that the email client never receives nor stores your Gmail password. OAuth also allows you to restrict access to certain data or to completely revoke access to individual apps as you like and at any time.
