[msmtp-users] How to send email with specified account name and attachment?

[Length Power <elearn2014@...20...>]

cat .msmtprc
account yahoo
tls on
tls_starttls off
tls_certcheck off
auth login
host smtp.mail.yahoo.com
user xxxx
from xxxx@...1...
password yyyy

account 163
host smtp.163.com
user zzzz
from zzzz@...449...
password wwww
auth login
tls off


There are two mail accounts
if i want to send email with account yahoo ,

cat demo_email | msmtp -a yahoo   xx@...450...

if i want to send email with account yahoo ,

cat demo_email | msmtp -a 163   xx@...450...

How to send email with specified account name and attachment?

The arguments in `man msmtp` contain no argument on attatchment.