When a new client registers on your client portal we send them an activation code to verify that the details they have provided are correct. By default, this activation code is sent to the client's mobile number. We have introduced an option to instead have the code sent to the clients email address. This is a setting which can be found under Setup> Client Portal> 'How to verify new clients identity on registration'.
If this setting is set to email the system will also send an email verification code when an existing client updates their details (ie email address or password) in the client portal.