If you come across the issue “exim dead but subsys locked”. Please try following steps.
root@server [/]# /etc/init.d/exim status
exim dead but subsys locked
exim dead but subsys locked
If you see this error check for a file named eximdisable in /etc/
If you found the file then do the following steps and you are all done.
root@server [/]# mv eximdisable eximdisable.bak
root@server [/]# /etc/init.d/exim restart
root@server [/]# /etc/init.d/exim restart