set smtp-use-starttls
set ssl-verify=ignore
set smtp=smtp://smtp.mail.com:587
set smtp-auth=login
set agent-shell-lookup-USER@HOST="gpg -d .password-store/smtp/smtp.mail.com.gpg"
set smtp-auth-user=username
set from="myname <username@mail.com>"

$ gpg -d .password-store/smtp/smtp.mail.com.gpg
gpg: encrypted with 2048-bit RSA key, ID 2F46870C, created 2016-01-12
      "myname <username@mail.com>"
PASSWORD

$ echo 'test' | mailx  -s 'test' uesrname@mail.com
Password: A password is necessary for SMTP authentication
"/home/nori/dead.letter" 1/8
... message not sent

$ mailx -V
v14.8.8