I've found what was the problem: in my SendGrid account there was Link Branding enabled. But that's little bit strange because it was enabled before moving to the new server and it worked fine.
This is a sad song, I forgot to backup the avatars and pictures uploaded by the user.
So I loss them all, and now them will be 404 when openning my site.
I only know about deleting fields of 404 in the database, but this workload is too much.
Who can tell me how to delete resources of 404 efficiently, thanks a lot.