A:AnswerThis is exactly the same printer as the M28w with the exception of the copy/scan function. So if the M28w was not compatible, neither will the M15w be. Having said that, both of them should work if you follow the setup properly as laid out here: https://support.hp.com/us-en/document/c04683559
A:AnswerYou can still print on envelopes, yes; making adjustments with your phone would be easiest with the HP Smart app, otherwise you may want to adjust the settings from a computer or tablet.