cURL speaks SMTP natively, so you could also send to a local SMTP server, or to the SMTP server in your email provider's MX records. (For emailing myself, I've never had much trouble sending mail directly to Gmail's MX records)

    curl --mail-from "you@gmail.com" --mail-rcpt "you@gmail.com"  --ssl-reqd --url smtp://aspmx3.googlemail.com -T <(echo -e 'From: you@gmail.com\nTo: you@gmail.com\nSubject: Curl Test\n\nHello');