Igros and the mikva

There is a certain Lubavitcher Chossid that works in the food business in Europe. Once, he got a small order from a frum family in a nearby city for some products. Being that the order was small, he told the customer that he won’t be making a special trip just to deliver the order. However, something came up and he was planning on making a big delivery 20 minutes away so he decided to go a little out of his way and provide the kosher food. Upon arrival at that house, the lady that ordered the food started complaining to him that her two daughters were married for some time already and neither had any kids. After thinking for a couple of minutes, he told the lady about how, even now, we are able to get brochos and answers from the Rebbe and introduced her to the concept of putting letters into Igros. After explaining and getting the lady to agree to do whatever the answer would be, she wrote a letter and looked up an answer online (being that no Igros were around). The letter that they “browsed” to said that the mikva that they were using wasn’t kosher – to make sure to go to a kosher mikva. (They were using the mikva in their city that had some shailos, the modern-Orthodox rav in the city ruled that it was kosher). He didn’t hear from the family for some time. The next time that he got an order from this lady, one of the daughters had twins and the other one had given birth as well. All due to the letter from the Rebbe