Post
Thanks to tourism and development of the Cambodian economy, postal service has improved dramatically compared to the time when the country was under the Khmer Rouge government.

All mails and posts abroad leave the country from Phnom Penh, so it's faster and cheaper if you send mails or posts from the capital city. If you send them from other cities or provinces, it'll take longer time and extra money.

If you intend to post valuable items, it's recommended to use courier or do it from another country. When posting mails or postcards, it's better to check with the staff of the post office and make sure they are franked before putting them into the post box. Mails and postal parcels sent to a country in Asia may arrive in a week or 10 days, those sent farther afield than Asia may take 2-3 weeks to arrive. Shipping is an alternative to posting, but would take up to 2-3 months to reach the destination. The shipping agent normally assists you with customs formalities if necessary. Shipping is by no means cheaper than posting.

Receiving mails and posts while traveling in Cambodia is not recommended due to unreliable and not always-on-time services.

Telephone & Fax
Cambodia country code (for calls from abroad to Cambodia) is 855
To make international calls you need to dial 001 or 007 first.
Areas telephone codes in Cambodia are as follows:
Banteay Meanchey: 054
Battambang: 053
Kampot: 033
Kandal: 024
Kep: 036
Koh Kong: 035
Kampong Cham: 042
Kampong Chnang: 026
Kampong Speu: 025
Kampong Thom: 062
Kratie: 072
Mondulkiri: 073
Oddar Meanchey: 065
Phnom Penh: 023
Preah Vihear: 064
Prey Veng: 043
Pursat: 052
Ratanakiri: 075
Siem Reap: 063
Sihanoukville: 034
Stung Treng: 074
Svay Rieng: 044
Takeo: 032

Making a domestic calls are generally cheap in Cambodia. You can make calls from hotels,  phone booths or card phone booths. Phone booths can be easily found throughout the urban areas.

If you want to spare the hassle of going out to phone booths or to local operators and if you have a GSM mobile phone with you, then you can acquire a SIM card and cards to charge your SIM cards and it's convenient that you can make the calls as you like. If your phone is registered the roaming service then it's even more convenient. Still you have to be very carefull , otherwise there'll be a hefty phone bills waiting for you at home.

The cheapest way to make an international phone call is via the internet. There are myriad internet shops in town of Phnom Penh, Siem Reap and other urban areas where you can make internet calls. The price is cheap, but the quality may not be clear and may be delayed or broken.

For sending and receiving faxes, you can go to the post office or an internet cafe.

Internet
Accessing the internet and email is very easy and inexpensive in Cambodia now. All internet cafes are easily found in major towns of Cambodia. The quality is great thanks to broadband connection. The traveller with laptop computer can also buy an internet card and hook up your computer to the phone line and can be ready to surf the internet. Many hotels offer wifi connection and some impose a charge for using it.