You could set the filename to a variable and execute sendmail on hangup, via the h
extension.
[outbound]
exten => s,1,Answer()
exten => s,n,Background(silence/1)
exten => s,n,ControlPlayback(/var/example)
exten => s,n,Set(filename=${callfile_name}${STRFTIME(${EPOCH},GMT-8,%m%d%y-%H%M)}.wav)
exten => s,n,Record(/var/${filename},0,5,qxk)
exten => s,n,Hangup()
exten => h,1,System(/opt/scripts/wavmail.sh ${filename} example_email@gmail.com)
/opt/scripts/wavmail.sh
(first argument is $1, second $2, ...)
#!/usr/bin/env bash
(printf "%s\n" \
"Subject: Example_Subject" \
"To: $2" \
"Content-Type: application/wav" \
"Content-Disposition: attachment; filename=$(basename $1)" \
"Content-Transfer-Encoding: base64" \
""; base64 $1) | /usr/bin/sendmail "$2"