[merlyn]

My two cents running a small to mid-sized email server service.

I do have a global block list based on certain gTLDs.

The list isn't one chosen at random based on the long list of gTLDs out there, but based on real time feedback from my honeypots, and my customer feedback reports, so SPAM getting through the other filtering techniques in use, usually with zero false positives on them.

Many of the gTLDs that are abused the most are ones that had fire sales in the past to get them off the ground.

As mentioned in other replies, .xyz is a SPAMers wasteland. That one would cause the most difficulty getting through anything.

The others that made my block list are probably not ones you would guess.

So, I wouldn't be too worried about things in general. None of the large providers do blocking on gTLD. Only a few smaller ones do. If the domain was sold for $1 getting-off-the-ground, it could have been picked up by the SPAMers cheaply for quick turnaround and abuse.