Praise be to Allah.
It is permissible to work in companies that deliver mail and parcels, if the material being distributed is permissible. As for haraam material such as alcohol, cigarettes, riba-based contracts and so on, it is not permissible to transport them or record them, or to help with them in any way, because that comes under the heading of helping others with sin, and Allah, may He be glorified and exalted, says (interpretation of the meaning):
“Help you one another in Al‑Birr and At‑Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression. And fear Allaah. Verily, Allaah is Severe in punishment”
This ruling is connected to knowing that there is something haraam inside the parcels, such as knowing that the parcel contains alcohol or cigarettes. But if it is not known what the parcels contain, there is nothing wrong with transporting them, organizing their movements and so on, because the basic principle is that it is permissible, unless it is the case that with some of the people from whom you pick up parcels, most of the time they contain haraam things, in which case it is not permissible to pick up parcels from them, based on what is likely to be the case.
It says in Kashshaaf al-Qina‘ (3/559): It is not valid to hire oneself out to carry dead meat and the like for people to eat who are not forced to do so, because that is helping in sin; but if it is being carried to people who are forced to eat it, then it is valid. It is not valid to hire oneself out to carry alcohol to those who will drink it, because the Prophet (blessings and peace of Allah be upon him) cursed the one who carries it and the one to whom it is carried. And no wage is to be paid to him, i.e., to the person who is hired to do something haraam, because of the reasons stated above. End quote.
The Standing Committee for Issuing Fatwas was asked: I work in the mail and transportation field. I work as a driver, distributing letters and so on to postal centres. In these bags in which the letters and so on are carried, there are occasionally glass bottles of alcohol which come from foreign countries. I do not know exactly where and when I am carrying these bottles of alcohol, because they come from abroad wrapped up inside the bags. I found out about that from a friend of mine. The transportation company has other centres which specialize in other things, such as transporting telephone equipment, wireless equipment, and other things. Please advise me: can I do this job without there being anything wrong, or should I resign or move to another centre in the mail and transportation field, such as the telephone centre and so on?
They replied: It is not permissible for you to transport the haraam things that come in the mail to other people if you know about them, because that is helping in sin, and Allah says (interpretation of the meaning):
“Help you one another in Al‑Birr and At‑Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression”
You have to look for another job, or move from this job to a place where nothing haraam is done. May Allah make things easy for you and help us all to do that which pleases Him. And Allah is the Source of strength. Blessings and peace of Allah be upon our Prophet Muhammad and his family and Companions. End quote.
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allah ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allah ibn Ghadyaan
Fataawa al-Lajnah al-Daa’imah
See also the answer to question no. 112902
And Allah knows best.