A number of factors can cause
Gmail not sending emails issue. This most common of which is your browser cache. If your browser is using a VPN to log into Gmail, you can accidentally block that service's servers. In order to fix this problem, you must disabling the VPN and then re-install it. This should solve your problem. Alternatively, you can clear the cache and history on your PC. Alternatively you can uninstall your VPN and reinstall it.
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