How to turn on offline mode in Gmail
Yes, even though Gmail is a web-based email service, it supports offline access when you have weak or no internet connectivity. Offline mode lets you view your past emails and attachments, up to 90 days. You can also compose new emails, and when you're back online, they will get sent.
To enable offline mode in Gmail, do the following:
Load up your Gmail inbox
Select the Settings Cog in the top right-hand corner
Select See all settings
Go to the Offline tab
Toggle Enable offline mail on
Click Save Changes
Gmail will now reload, and offline access will now be enabled. Don't forget to save Gmail to your bookmarks and next time you are offline head to Gmail to access your emails.