No, because that does more harm that good.
The point is that IPs are today almost always given out dynamically, so you would just block the next unlucky chap who got that IP from his ISP a day after the offender. What it will get is word blocking,though: you give it a list of words, and if one of these is found in the message, it is rejected.
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Will flatPHPbook feature IP blocking in the near future?
No, because that does more harm that good.
The point is that IPs are today almost always given out dynamically, so you would just block the next unlucky chap who got that IP from his ISP a day after the offender. What it will get is word blocking,though: you give it a list of words, and if one of these is found in the message, it is rejected.