Gmail is free, would you be happy if they updated it and your email didn't work anymore? I love OpenBSD but they constantly change the rule syntax for pf, which invalidates huge swaths of forum posts and other online documentation, even published books. The man page doesn't contain every conceivable explanation and example for every scenario either, nor could it, so that is also not a solution. Whether or not the price is free, the use is not, as it requires hours of valuable time to implement.