PS: There have been some attempts at setting up change-of-address
services where you can register old and new addresses, so mail servers
could query them after getting a 550, and they never went anywhere either.
See US Patents 6,654,789, 6,892,222, and 7,080,122.
By the way, 6,654,789 expires a week from Monday and 6,892,222 expired
last year so if you find any good ideas in them, you can use them.
7,080,122 doesn't expire until 2023.
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