# Fixing Sendmail
 
 If Sendmail is not behaving as expected or hangs during installation, it might be because FQDN is not set. 
 
 Perform the following steps:  
 
 1. Set an FQDN for your Photon OS machine. 
 
 1. Run the following commands in the order below: 
         
     ```
     echo $(hostname -f) > /etc/mail/local-host-names
         
         cat > /etc/mail/aliases << "EOF"
             postmaster: root
             MAILER-DAEMON: root
             EOF
     
         /bin/newaliases
     
         cd /etc/mail
     
         m4 m4/cf.m4 sendmail.mc > sendmail.cf
     
         chmod 700 /var/spool/clientmqueue
     
         chown smmsp:smmsp /var/spool/clientmqueue
     ```