I get this error with stock email settings in Laravel 5.1 Homestead when I try to send a password reset mail.
Swift_TransportException in AbstractSmtpTransp
In Laravel 7 , your .env file should be like this
MAIL_MAILER=smtp
MAIL_HOST=smtp.mailtrap.io
MAIL_PORT=2525
MAIL_USERNAME="your username"
MAIL_PASSWORD="your password"
MAIL_ENCRYPTION=tls
#MAIL_FROM_ADDRESS=null
#MAIL_FROM_NAME="${APP_NAME}"
Make sure these two lines are commentout like this...
#MAIL_FROM_ADDRESS=null
#MAIL_FROM_NAME="${APP_NAME}"
Final step: run these step of command in your terminal to successfully send notification -
php artisan config:cache
php artisan cache:clear
php artisan config:clear