Can I print postage on labels without a fluorescent stripe and use them on envelopes?
No, labels without a fluorescent stripe cannot be used on First-Class Mail® envelopes. In order to process mail properly, envelopes printed with PC Postage indicia are required to have a facing identification mark (FIM). There are two types of facing marks that are allowed with envelopes: a label with a fluorescent stripe or the small vertical bars that print just to the left of the indicium when printing directly on an envelope. Note that this requirement does not apply to packages or flats.
