1. Just a letter from the husband or his attorney does not mean real Islamic Talaq unless Talaq has been pronounced properly in front of two pious witnesses along with all other conditions of Talaq ( Husband should not be forced to divorce, wife should not be passing her menstrual period, etc)
2. Iddah of Talaq is obligatory on the wife for three periods of menses or three months after she knows about Talaq, no matter how much time they were separated.
3. If the wife is old enough that she has no menstrual period at all, then she has no Iddah after Talaq.
4. If the marriage was only been recited but never consummated, then no Iddah after Talaq.