The mobile operator's bills, statements and letters will feature a variety of targeted promotions for handsets, tariffs and services.
The initiative has removed the need for separate leaflets, offers or other marketing collateral within the envelopes.
Orange believes the personalised communications will boost business because most customers read their phone bills, rather than immediately discarding them. As many customers will file their statements, the promotions may be read again at a later date.
The introduction of the activity follows the signing of a three-year deal between Orange and transactional-mail specialist DSTi Output, which has taken over the printing of Orange's essential communications.
Earlier this month, Orange launched its Christmas ad campaign. The £9m work, created by Fallon, takes the theme of 'togetherness'.
The TV ads feature two wind-up toys joined at the hip, and tell viewers they should stay in touch throughout the year, not just at Christmas.
The campaign, which is being supported by a range of direct communications created by bd-ntwk, will be used as an umbrella concept to promote Orange's services.
According to Nielsen Media Research, Orange spends more than £90m on marketing in the UK each year. The biggest spend is on TV, which accounts for £22m.