Post
The government-run postal service in Laos is fairly inexpensive compared to local standards. From major tourist destinations such as Vientiane and Luang Prabang, sending and receiving mails/parcels/letters is fairly easy and reliable. But if you travel in remote areas and want to send/receive letters/parcels, then it may not be that reliable.

If you are on a tour and in no hurry, you may want to wait and post your letters/parcels from Thailand or Vietnam. Post Office is normally open from 08:00 A.M through 09:00 P.M, 7 days/week in Vientiane and Luang Prabang. In the case you need to send/receive urgent letters/parcels, then the EMS or courier service is recommended, but it is more expensive.

When posting parcels, you must leave it open for inspection before posting. The same procedure is applied when you receive a parcel. A fee may be applied for such service. It may take up to 2 months for a letter/parcel to reach the destination.
 
Telephone /Fax
The GPO offers public telephones for local, national and International Direct Dialing Calls. Phone cards are available at many shops, phone booths are available for domestic and overseas calls. Most large hotels have IDD lines, but calls from a hotel are very expensive. At Post Office and some hotels, sending/receiving fax service is also available.

If you have a GSM hand phone, then you can acquire a SIM card from a local shop. Signals for mobile phone are available at major tourist destinations like Luang Prabang, Vientiane or Savanakhet.

To make a phone call within the province/city, dial the phone number only.
To make a phone call to another province, dial 0+the phone number
To make an international phone call, dial 00 +country code + area code + phone number.
Lao country code is 856.

Lao area code:
Attapeu  36
Bokeo   84
Bolikhamsai    54
Champasak    31
Hua Phan  64
Huay Xai  84
Khammuan    51
Luang Nam Tha  86
Luang Prabang  71
Paksan  54
Pakse   31
Phongsali  88
Sainyabuli  74
Salavan  34
Sam Neua  64
Savanakhet    41
Sekong  38
Tha Khaek  52
Udomxai  81
Vang Vieng   21
Vientiane City  23
Vientiane Province  21
Xieng Khuang 61

Email/Internet
There are many internet cafes which provide easy access to the internet and reasonable rates at most tourist destinations such as Luang Prabang,  Vientiane, Pakse, Savanakhet...Even though internet speed may be very slow sometimes.