Bigmir switched to Gmail

Yesterday at the entrance to the mailbox from the largest Ukrainian portal Bigmir, my friend discovered that her old mailbox was replaced by a mailer from Google, only on the domain Bigmir.net.
The mailbox is completely identical to Google, only instead of contextual advertising Bigmir put a banner.
See screenshots under the cut.




The question is, why do we need a second mail from Google? Why do we need these clones?