Linux Send mail fails sendmail 354 enter mail end with . on a line by itself

To we are not getting any Oracle alert mail from the monitoring script
so when i run the script manually we are getting below error from Linux.

Error like below:

sendmail 354 enter mail end with . on a line by itself

and when /var/log/maillog
stat=Deferred: 452 4.3.1 Insufficient system resources

Solution:

Check the exchange server setting for the account and clear the space for the account then recheck.