Is it correct to write 'Dear Sirs' when you are sending email

DEAR GUESSING GROUP dear number The Nagaland State Lottery Department has released today's results Check your today's fortune result Dear Lottery Result Today 1pm 1st Prize is dear lottery online Dear Customer, Our Bank's Customer Care Toll Free Numbers are 1800-890 Account Number, Cheque Number, Cheque Date, Cheque Amount, Transaction Code

dearlotri Dear SirMadam: If you know you are writing to more than more than one unknown gender persons: Dear SirsMesdames: