In the .env file in the web root you will find the email related configuration:

# Supported drivers: "sendmail", "smtp" and "mailgun"
# https://laravel.com/docs/6.x/mail
# For simple and reliable email we recommend https://sendgrid.com/
# When using sendgrid, use MAIL_DRIVER=smtp
MAIL_DRIVER=sendmail
MAIL_HOST=smtp.sendgrid.net
MAIL_PORT=465
MAIL_ENCRYPTION=ssl
MAIL_USERNAME=apikey
MAIL_PASSWORD=null

# Only when using Mailgun
# The values can be api.mailgun.net, api.eu.mailgun.net or api.us.mailgun.net
# depending on the region you selected in the Mailgun dashboard.
MAILGUN_ENDPOINT=api.mailgun.net
MAILGUN_DOMAIN=mg.mymailgundomain.com
MAILGUN_SECRET=