Is it permissible to invest savings in "El-Bosta" (the Post Office), and are its profits permissible (halal)? And is it permissible to keep the principal and donate the profits if they are not permissible, or is it better to keep it as a deposit without profits?

It is forbidden to deposit money in a savings account, as it is usury (riba), which is prohibited. This is because a known percentage is added to the principal. Moreover, the postal service deposits the savers' money in usurious banks. Even if the money were invested, deducting a known amount from the principal is forbidden. A Muslim must avoid dealing with savings accounts and usurious banks, because Allah has threatened those who consume riba with war. Allah Almighty says: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged." The Prophet, peace be upon him, said: "A dirham of riba that a man consumes knowingly is worse than thirty-six acts of fornication." The Messenger of Allah, peace be upon him, also cursed the one who consumes riba, the one who feeds it, its two scribes, and its two witnesses. It is not permissible to place money in savings funds, even without profits, except out of necessity. It is also not permissible to take its interest and distribute it for charitable causes. Whoever has engaged in these accounts must withdraw immediately and dispose of the usurious profits by giving them to charitable causes. He is only entitled to his principal.