sender name same as recipient name

Sorry if this is a well-known issue... first I have encountered it.

I am using SA 3.1.9 installed on a CentOS Linux system.

One of my clients just noticed a huge spike in spam getting
through, even though SA is turned on for his email account at
sensitivity level 4.

For the sake of anonymity, let's say my client's domain is blah.com.

His address is mark@blah.com.  99% of the spam emails
he received during this spike were from mark@something.com
(where "something" represents various domains.)

Question: is SA not filtering out these obvious spams because
the name "mark" is the same as the name on my client's
account?

thanks,
Feral