Flag for indicating if the isEmail function should perform a DNS check or not.
If set to CheckDns.no, isEmail does not perform DNS checking.
Otherwise if set to CheckDns.yes, isEmail performs DNS checking.
See Implementation
Flag for indicating if the isEmail function should perform a DNS check or not.
If set to CheckDns.no, isEmail does not perform DNS checking.
Otherwise if set to CheckDns.yes, isEmail performs DNS checking.