What is the ruling on working as a mail carrier in Sweden, given the presence of some forbidden items in the distribution center? Does this fall under the principle of "hardship brings ease"? And what should I do if the mail contains forbidden items?

There is no harm in working as a postman, provided that he avoids delivering visibly forbidden items, such as gambling magazines, or if he knows that a package contains alcohol, due to the Almighty’s saying: ﴿And cooperate in righteousness and piety, but do not cooperate in sin and aggression.﴾ As for sealed letters and packages, and magazines and advertisements that are predominantly permissible, any forbidden content within them is excused if it was not the intention, due to widespread affliction.