I am having problems with someone spoofing emails from my server for spam. What happens is that I start getting reject and bounce notices in the mqueue and it is bringing my server to it's knees (I just upgraded to a faster server also). For example, yesterday in a matter of seconds the mqueue went from 13 to 1800 queued messages before I stopped sendmail.
Does anyone have any advice to handle this situation? My server becomes extremely slow or even inaccessable during these episodes.
It seems to me that Sendmail should be smart enough to look at the email address domain and check the IP address to ensure that the domain and IP agree before sending a bounced or SPAM message.
I was surprised that the Barracuda appliance doesn't do this because many of the messages are from Barracuda.