From the Settings screen click on the Offline option as shown in the below image.
From this Offline menu, enable Offline Mail. After doing this, you will reach a screen with options as shown in the image below.
Now, select the emails to get synced, download attachments, and store emails offline when you log out of your Gmail account that is synchronized for offline storage.
Note: For anyone who shares their system with someone else, should make sure to erase/delete all sync messages after signing out of the account to avoid any security and privacy breaches.
After selecting saving offline data or not, click on the Save changes button.
Now, to use Gmail in an offline mode, you need to open a Gmail tab in Chrome and leave it open even when you are offline.
Gmail will automatically sync your most recent emails for offline access and keep them for a set amount of time, ranging from 7 days to 90 days when the offline mode is activated.
Gmail will send all of your emails to your outbox and download a light version of any incoming emails as soon as your computer has an active internet connection, regardless of how erratic it may be. Do keep in mind that you will require an active and reliable connection to download attachments.
It is advised to bookmark your inbox in Chrome to make accessing your email offline easier by clicking on the star icon available to the right of the address bar. You can also remove all your offline data and turn off the Gmail offline mode whenever you want. If you use Gmail with your work or school account, you can ask your admin to assist you in changing your settings.
Besides, you won’t be able to use your Gmail if it’s not loaded already after you get out of the internet zone.