Here is a thing
Why mail bounce?
1. server name is wrong
2. user name is wrong
if Server name is wrong you cannot send the email at all
But if the user name does not exists then you might get 550 message, here is a paragraph copied from RFC2821
However, in practice, some servers do not perform recipient
verification until after the message text is received. These servers
SHOULD treat a failure for one or more recipients as a "subsequent
failure" and return a mail message as discussed in section 6. Using
a "550 mailbox not found" (or equivalent) reply code after the data
are accepted makes it difficult or impossible for the client to
determine which recipients failed.
and about moving to junk mail: as a matter of fact think junk mail as a directory, you can move your email to any directory to sort, but there is no reason for the sender to know where it moved. same about junk mail mover. Server wont give you any information about being moved to junk mail.