Message not sent. Server replied:
Unknown response
435 Unable to authenticate at present

If you are getting the above error message do the below Steps,

Login as a root Root via shell

[root@server ~]# /scripts/eximup –-force
Before executing the command check the attribute of file
/etc/exim.conf If yes, then remove attribute and and execute the command.
[root@server ~]# lsattr /etc/exim.conf (check the attribute)
—-i–a-u— /etc/exim.conf
[root@server ~]# chattr -iau /etc/exim.conf  (to remove the attributes)
[root@server ~]# lsattr /etc/exim.conf
————- /etc/exim.conf

That’s it you have all done 😀