A license key is a unique alphanumeric code used to verify that you have a legitimate, paid subscription to . While the core version of the plugin is free to use, the Pro version requires a license to unlock advanced features such as email logging, advanced email routing, and white-labeling options.
WP Mail SMTP offers several pricing plans tailored to different user needs, from individual bloggers to large agencies. Verifying Your License - WP Mail SMTP Pro wp mail smtp license key
Note: Prices are approximate and subject to change. Lifetime licenses are not offered; all are annual subscriptions. A license key is a unique alphanumeric code