I had set up a domain email address to forward to an address containing a plus sign; e.g., mylogin+variation@gmail.com. After the transition it became myloginvariation@gmail.com, which would not reach the intended recipient.
Fortunately, in my case, the domain address was unlikely to get used. Others may not be so fortunate.
Fortunately, in my case, the domain address was unlikely to get used. Others may not be so fortunate.