Originally ran as 155 dn by 156 up it was originally started by Northeast Frontier Railway which is called NFR in short. Later on, the primary maintenance was transferred to the Delhi Division of the Northern Railway and ran under the numbers 14056up by 14055 dn. The train recently got LHB rake and the primary maintenance went back to NFR with Dibrugarh being the maintenance station. Once the pride of NFR with neon lights in its first class compartments and has eight cushioned sleeper class coaches in the 1970s, the train went to a sharp decline both in priority and facilities with conditioning of its rake worsening. However, with the new LHB rake trying to get its lost glory back. The up train belongs to Northeast Frontier Railway zone. Northeast Frontier Railways decided it will be running as 15955/15956 Brahmaputra Mail from 9 December 2019.^[1]

• 15955 departs Dibrugarh every day at 23:25 and arrives at Delhi Junction at 6:05 on the fourth day from departure (e.g.:the train which departs Dibrugarh on Thursday at 23:25 would arrive at Delhi on Sunday at 6:05) covering a distance of 2,596 km (1,613 mi) in 54 hrs and 40 mins with an average moving speed of 48 kilometres per hour (30 mph)
• 15956 departs ld Delhievery day at 23:40 and reaches Dibrugarh at 4:25 on the fourth day (e.g.: the train departing DLI at 23:40 on Thursday would reach DBRT on Sunday early morning at 4:25) covering a total distance of 2,596 km (1,613 mi) in 52 hrs and 45 mins with an average moving speed of 48 kilometres per hour (30 mph)^[2] But W.E.F. 20/12/2020, this train will run between Kamakhya Junction & Old Delhi, covering 2,025 km (1,258 mi) in 38 hrs 00 mins on the 3rd day as 15955 (e.g.: the train departing KYQ at 14.35 hrs on Thursday would reach DLI on Saturday early morning at 04:35 hrs) with an average moving speed of 53 kilometres per hour (33 mph). In return the train will run between Old Delhi & Kamakhya Junction, covering 2,025 km (1,258 mi) in 38 hrs 00 mins on the 3rd day as 15956' (e.g.: the train departing DLI at 23:40 hrs on Thursday would reach KYQ on Saturday afternoon at 13.40 hrs) with an average moving speed of 53 kilometres per hour (33 mph)

The train has both AC and non-AC class of accommodation. The composition of this train is

After the completion of electrification, from 22/10/2021, this train is running end to end from Old Delhi to Kamakhya hauled by a Ghaziabad-based WAP-5 / WAP-7 locomotive.

The train runs from

• Kamakhya via
• Rangiya Junction
• Barpeta Road
• Bijni
• New Bongaigaon Junction
• New Alipurduar
• New Cooch Behar Junction
• Falakata Railway Station
• Dhupguri railway station
• Jalpaiguri Road railway station
• New Jalpaiguri (Siliguri)
• Kishanganj
• Dalkhola
• Malda Town
• New Farakka Junction
• Barharwa Junction
• Sahibganj Junction
• Bhagalpur Junction
• Jamalpur Junction
• Kiul Junction
• Patna Junction
• Ara Junction
• Pt. Deen Dayal Upadhyay Jn.
• Mirzapur
• Prayagraj Junction
• Kanpur Central
• Tundla Junction
• Aligarh Junction to
• Delhi Junction railway station.^[3]

• This is one of the oldest-running trains of this zone. This train is known for its amount of defense personnel using this train.
• This train was also involved in three major railway disasters in Indian history. One was the bombing of the train between Kokrajhar and New Bongaigaon in December 1996 by Bodo Militants, and second was the Gaisal Rail Disaster, a head-on collision between Avadh Assam Express and Brahmaputra Mail.^[4] The third one occurred on November 22, 1985, when this passenger train (then known as Tinsukia Mail ) and a freight train collided in the eastern state of West Bengal, at Dhupguri railroad station, about 750 miles east of New Delhi killing at least one person and injuring more than 300 others, seven seriously. Three to Five cars of the passenger train derailed in the accident.^[5][6]