ummm, if you have emailed your critter or senator, your email address was captured and since they all use the same series of servers those email addresses are “available” for lookup and use.
Apparently that is what may be happening, it happened to me. My question is, however, is that legal?
No. The White House and Congress do not share computer systems, let alone servers. What’s more, the House and the Senate have separate systems and do not share servers, either. Of course that does not preclude individual members, or, say the Democrat Conference, from providing the White House with lists. But there is no direct access, and Congress guards its systems and servers like a hawk.