Hard spam email box. I want to understand how?

Question

Email

About 10 days ago, a hard spam of one of my email addresses began. Letters come from different email addresses, from different servers, with different subjects and a bunch of characters in the message body. There is only one thing in common:
X-Mailer: Chilkat Software Inc ( http://www.chilkatsoft.com)
It does not give me any inconvenience, I put a filter that extinguishes everything on the server. But, I wonder how such a wave was organized. Spam comes from real mailboxes, selectively checked if they exist.
PS Already more than 300 thousand letters have come and this, apparently, is not the end.

Answer 1

Someone persistently suggests that you create your own spam list from these 300 thousand addresses and sell it. Probably, this is a gift for some holiday from your friends.

Answer 2

If the boxes exist, there is no fact that they were sent from them. You can put addresses...

Answer 3

Chilkat is a fairly well-known office. Components for .net writes: www.chilkatsoft.com
Do you have an enemy programmer-dotnet bot driver?