There's not a simple and direct way to do this; but it can be done with a couple of steps.
Successful VPN connections do result in a syslog messages (722022 is the message-ID for connection). So, if you have logging enabled, you can setup an action to log syslog messages (filtered only to include the message(s) of interest) to a defined SMTP server.
Here's a detailed guide showing how to do this:
https://www.cisco.com/c/en/us/support/docs/security/pix-500-series-security-appliances/63884-config-asa-00.html#anc19
