The Post Office has identified 25 branches across the Newport and Gwent Valleys area for possible closure as part of its UK-wide network review.
"Changing lifestyles" has had an effect on post office use
The proposals also include establishing three new outreach service points, two in Chepstow and one in Caldicot.
A six week public consultation on the plans has been launched.
The latest announcement follows a closure list of 31 post offices in Cardiff, Bridgend, Vale of Glamorgan and valleys issued last October.
The plans will leave 126 post offices in the Newport and Gwent valleys but the company insists more than 99.6% of the area's population will either see no change, or will remain within a mile of an alternative branch.
Meanwhile, a partnership with newsagent WH Smith has safeguarded the future of services in Cwmbran.
Steve Geraty, Post Office Ltd's network development manager for Wales, said closing any branch was always very difficult.
"The Newport and Gwent Valleys are diverse in nature - from the densely populated urban areas of Newport, Cwmbran and Caerphilly to the former industrial valleys including the towns of Ebbw Vale and Tredegar to rural Monmouthshire.
He added that 63 branches are set to remain in rural areas, where 48% of the population live, and another 63 in urban areas, which serve 52% of the population.
Abertillery: Cwm Celyn; Princess Street
Tredegar: Dukestown, Georgetown
Ebbw Vale: Rassau, Winchestown
Hengoed: Caerphilly Rd, Penpedairheol, Penybryn
Blackwood: Argoed, Wyllie
Newport: West End, Wattsville, Christchurch Road, Malpas Road, West Park
Abergavenny: Govilon, Llanellen
Pontypool: Pentwyn, Penygarn, Pontnewynydd, Penygraig Terrace
Source: Post Office Ltd
He said the company had given consideration to the needs of those living in "communities defined as deprived".
Mr Geraty said: "This proposal for future network provision in Newport and Gwent valleys provides for 18 branches being located in urban deprived communities."
Post Office Ltd said it had already consulted with the watchdog Postwatch and local authorities.
It is believed around 197 post offices closures are likely in Wales during 2008.
The plans are part of a wider restructuring of Post Office services throughout the UK, as part of changes in technology and "changing lifestyles.".
About 2,500 post offices - a fifth of those left in the UK - are to close by 2009.
The public have been given until 25 February to comment.