SMTP_SETTINGS = {
  address: ENV.fetch("SMTP_ADDRESS"), # example: "smtp.sendgrid.net"
  authentication: :plain,
  domain: ENV.fetch("SMTP_DOMAIN"), # example: "heroku.com"
  enable_starttls_auto: true,
  password: ENV.fetch("SENDGRID_PASSWORD"),
  port: "587",
  user_name: ENV.fetch("SENDGRID_USERNAME")
}

SMTP_SETTINGS = {
  address: ENV.fetch("SMTP_ADDRESS"), # example: "smtp.sendgrid.net"
  authentication: :plain,
  domain: ENV.fetch("SMTP_DOMAIN"), # example: "heroku.com"
  enable_starttls_auto: true,
  password: ENV.fetch("SMTP_PASSWORD"),
  port: "587",
  user_name: ENV.fetch("SMTP_USERNAME")
}

--- 
+++ 
@@ -3,7 +3,7 @@
   authentication: :plain,
   domain: ENV.fetch("SMTP_DOMAIN"), # example: "heroku.com"
   enable_starttls_auto: true,
-  password: ENV.fetch("SMTP_PASSWORD"),
+  password: ENV.fetch("SENDGRID_PASSWORD"),
   port: "587",
-  user_name: ENV.fetch("SMTP_USERNAME")
+  user_name: ENV.fetch("SENDGRID_USERNAME")
 }
Update ENV username & password
