How to make mail command to send email to root after installing msmtp?

Install a simple SMTP client: sudo apt install msmtp msmtp-mda Set in msmtprc :: cat .msmtprc account default host smtp.qq.com from x1@qq.com auth on tls on tls_certcheck off user x1@qq.com password xxxx logfile ~/.msmtp.log I can send email with qq account. echo "Testing msmtp " | mail -s "hi root" -r x1@qq.com -- aa@yahoo.com The email can be found in yahoo email. I find a new issue that user can't send email to root in system! echo "cron task work done " | mail -s "hi root" root mail: cannot send message: Process exited with a non-zero status Check the log: Aug 24 20:47:31 host=smtp.qq.com tls=on auth=on user=x1@qq.com from=debian@debian.debian recipients=root@debian.debian smtpstatus=501 smtpmsg='501 Mail from address must be same as authorization user.' errormsg='envelope from address debian@debian.debian not accepted by the server' exitcode=EX_DATAERR echo "cron task work done " | mail -s "hi root" -r debian@debian.debian root The log info: Aug 29 06:56:39 host=smtp.qq.com tls=on auth=on user=x1@qq.com from=debian@debian.debian recipients=root@debian.debian smtpstatus=501 smtpmsg='501 Mail from address must be same as authorization user.' errormsg='envelope from address debian@debian.debian not accepted by the server' exitcode=EX_DATAERR Everytime mail command was called ,it relay to external host smtp.qq.com enven if i specify return host as debian@debian.debian,how can make mail command send email between user and root in the system? I find that postfix or exim4 will be removed when to install msmtp-mda,the fact maybe realted with my issue.