SendGrid (now owned by Twilio) is used by some of the biggest names in the industry such as Uber, Spotify, Yelp, Airbnb, and even Kinsta. It originally started out as a transactional email SMTP and API serviced designed for developers. However, they now also offer email marketing features as well.
Click the Create API Key.
From the dialog select Restricted Access
Enable the option Mail Send -> Mail Send
Once the API keys generated, please keep them in a safe place. You can’t get the same key again and you need to regenerate a new key.
Please use the following SMTP configuration in your application.
|Port||587 or 465(SSL)|
|Username||apikey (Yes. apikey is the username for all accounts)|
|Password||API key generated in the above steps|
Please find the sample C# application in the below link.