your problem seems to be email related
You may be able to connect on the server "blindly" i.e. ignore that error message, and type your log in and password, then stop your email service.
if the boot sequence waits for email service to complete it's startup before going to the next service, and eventually letting you log in, then maybe you can reach your server via ssh (IP and ssh services are probably started before email service).
And lastly, you could boot on a live CD, mount your system disk, and disable launching that email service by editing the appropriate file.
GOOD LUCK !!!