Definitely! Technically, this can be a very usefull addition to IP Filter,
The cost of packet payload scanning will be much greater CPU load vs header scanning, right?
This is certainly the case in SMTP envelope rejecting (after RCPT TO) vs SMTP DATA scanning.
And with the SMTP DATA scanning, I've seen huge differences in efficiency of OS POSIX regex vs a 3rd party PCRE regex lib.
Len
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