The system itself checks the addresses of clients and if it detects a nonexistent one, adds it to the list of nonexistent addresses. As a result, the same address could be both in the white list, where the user added it, and in the list of nonexistent addresses. This created difficulties when sending letters because if a user tries to send a letter to a nonexistent address, it does not go away. Instead, the letter is highlighted in yellow and turns into an internal comment — the user does not understand what is happening. To send letters to such addresses, the user had to clear the list of nonexistent addresses manually.
Now, before adding an address to the list of nonexistent addresses, the system checks if it is on the whitelist. If not, it adds; if there is, it skips. And in the request card, you can see in which list the address is located — next to the address, there is a warning icon; when you hover over which a hint pops up: