Can I bounce a range of IP addresses?

You could try to write a filter, and if you look at the list of available actions, one of them is "Reject with reason".  You could try blocking the TLD like ".ru" or whatever.  I haven't tried it, but you can put in any reason you like such as "Not our customer" or other common bounce messages.  But if all these messages are just spam, no one is going to read a bounce anyway.  I would just go for "Discard" so that you never see them.

Thanks for the answer and sorry for the delayed response. To be specific, I'm trying to do this at the Comcast level, i.e. have their email server bounce before it's sent to my inbox.

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@banderson1962 wrote:

Thanks for the answer and sorry for the delayed response. To be specific, I'm trying to do this at the Comcast level, i.e. have their email server bounce before it's sent to my inbox.

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I don't think so, but I don't know for sure.  You could call Comcast security and ask.  If anyone knows they would------------------

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