A printer includes a memory storing instructions for authenticating a login user and determining whether a user identity information is included in a print data. When the user identity information is included in the print data, the instructions cause the printer to determine whether the login user is identical with a data sender user having sent the print data. When the login user is identical with the data sender user, the instructions cause the printer to print the pint data. When the login user is not identical with the data sender user, the instructions cause the printing portion to not print the print data. When the user identity information is not included in the print data, the instructions cause the printer to print the print data irrespective of whether the login user is identical with the date sender user.