The courier service authorities have been instructed to cross-cheek addresses of senders and receivers before taking and receiving any booking.
Police said they were fearing that explosive substances could be transported to different areas of the country under the names of different companies.
Intellectuals of the country were also threatened by using the names of some companies who later could not be identified.
Upon intelligence report, Dhaka Metropolitan Police (DMP) Commissioner Asaduzzaman Miah gave written instructions to the courier service authorities.
Meanwhile, many courier companies said they could not check the envelop on ethical ground. They, however, said they would follow the instructions of the DMP.
DMP spokesperson and Deputy Commissioner (media and public relation) Muntasirul Islam told the Dhaka tribune that professors, writers, bloggers, publishers were being threatened by militants or miscreants by sending letters through courier services.
Police, while investigating, could not trace the addresses of some senders as those were wrong addresses, he said.
President of Courier Service Association of Bangladesh Hafizur Rahman Pulok confirmed receiving the letter. “We received the letter with some written instructions from the police commissioner’s office some 20 days back.” He said the instructions had already been conveyed to the association members and initiated taken.
General Manager of Sundarban Courier Service Delwar Hossain said under the Postal Office Act 1898 a company never opens the personal or official letter on ethical ground but it can check a parcel if it grows any suspicion in their minds.
On November 25, at least 10 priests of different churches in Rangpur district received death threats in letters sent through courier service. The next day they filed a General Dairy with the police station concerned.
Reverend Barnabas Hemron, pastor of Rangpur Baptist Church located in the divisional city, received the letter.
On May 20, Dhaka University Vice-Chancellor AAMS Arefin Siddique and several other teachers received letters that threatened to kill them.
The letters, containing a list of 10, were apparently sent by al-Qaeda and Ansarullah Bangla Team 13.
Prime Minister’s Political Affairs Adviser HT Imam’s name was on the top of the list.
The others include Gonojagoron Moncho spokesman Imran H Sarker, writer-teacher Muhammed Zafar Iqbal, Dhaka University teacher Kaberi Gayen, Jagannath Hall Provost Ashim Sarker and Awami League MP Tarana Halim.