Instagram is enabling an harassment attack.
They are sending out "change in terms of use" statements, you've
probably received it.
Apparently they will send them to unconfirmed accounts, en masse.
So for example you own example.com and all email for *@example.com
goes to you.
And there are no legitimate email accounts for that domain so can't
possibly be confirmed accounts.
So you are receiving a firehose of "terms of use" emails to
randomstring@example.com apparently being generated by a script,
random+domain@domain like (from the actual emails tho not
example.com):
qiuncjhuxeexample@example.com
mazhjkmthexample@example.com
and so on and so on, each one different.
SOLUTION: Stop sending your terms of use update messages to
unconfirmed accounts. It's a trivially abused harassment vector as
we're seeing.