Complete/correct exim server configuration method General debian hosts have installed exim. If not, run apt-get install exim4 configuration method 1 first: run dpkg-reconfigure exim4-config first option select first: internet site; mail is sent and stored ed directly using SMTP second option input: method 2: vim/etc/exim4/update-exim4.conf.conf dc_eximconfig_configtype = 'internet' # corresponding to method 1 first dc_other_hostnames = 'your IP corresponding DNS name' and then restart the exim service: invoke-rc.d exim4 restart Modify/var/log/exim4/folder permission: chown-R Debian-exim/var/log/exim4chmod-R u + rw/var/log/exim4 (optional) try sending an email: echo "mail content" | mail email address s = "mail title" to check the number of sending processes: exim-bpc delete emails in the sending process: exim-bpru | awk {'print $ 3'} | xargs exim-Mrm if an error occurs: mkdir-p/var/log/exim4touch/var/log/exim4/mainlog no error is reported