I heard of many poskim that disagree with reb moshe which ones agree? If you look in igros moshe he says that you should not realy on his heter only in extreme cases.and if you look on the OU website they write that todays problem is very diffrent and reb moshes heter doesnt even apply b.c of changed gov reg....i was shocked when i read it???
Responsa Radbaz (4, 75), Peri Chadash (Yoreh Deah 115, 6), and Aruch Hashulchan (Yoreh Deah 115, 16), all agree that the decree on milk which was milked by a gentile without Jewish supervision applies only when there is an actual concern that forbidden milk was mixed in, but in a case where there is no such concern it is permitted. This is like the opinion of the Igrot Moshe. Rabbi Moshe Feinstein himself testifies (in Igrot Moshe Yoreh Deah 1, 47) that most Torah observant people and many rabbis are lenient in this matter. Also the Chazon Ish (Yoreh Deah 41, 4) writes like the opinion of the Igrot Moshe that when there is government control on the milk, and if one will mix impure milk he will be subject to a penalty, this is included in the Halachic term of Mirtat (fear of penalty which insures no violation). You can review this subject in detail in the sources I mentioned in my previous answer: Sefer Hakashrut of Rabbi Fuchs chapter 8 sections, 9, 13, 14 and in the footnotes. Igrot Moshe Yoreh Deah 1, 47-49. Regarding what you wrote that "If you look in Igrot Moshe he says that you should not rely on his Heter (permit) only in extreme cases " – I think there must be some misunderstanding here. Rabbi Moshe ZT"L writes explicitly that one who wants to rely and be lenient has a very good reason for it and is entitled, and one who wants to be lenient is doing right according to Halachah. For the benefit of this subject I will translate his words precisely (Igrot Moshe Yoreh Deah 1, 47) one who wants to rely and be lenient has a very good reason for it and is entitled as most Torah observant people and many rabbis are lenient in this matter. And G-D forbid to say that they are doing wrong according to Halachah. Nevertheless it is appropriate for Baalei Nefesh to be stringent and there is no concern of arrogance. I am also stringent for myself, but one who wants to be lenient is doing right according to Halachah and should not be considered disrespectful to prohibitions. In regard to what you wrote that "if you look at the OU website they write that today's problem is very different and Rav Moshe's Heter (Halachic permission) does not apply because of the change in government regulations" - I cannot relate to this if I have no exact source. However, we can say as follows; the Kashrut authorities of the OU actually give Kashrut to milk which is not Chalav Yisrael. Are you familiar with the products marked with OU/d? I'm sure they would not do this if they thought it was not kosher today. Perhaps you are referring to the important note which appears at the end of the article "Kosher in the dairy case" by Rabbi Sheldon Blech in the following link: http://www.oukosher.org/index.php/articles/single_print/10 Travelers beware: The Heter (permission) to use non-supervised milk applies only in countries where the government maintains strict controls on the milk supply. There are a number of countries where governmental control is weak, and effective enforcement of food regulations is non-existent. In addition, non-kosher milk such as mare’s milk is a staple in certain parts of the world, and its availability could compromise any general assumptions as to the kashruth of the milk supply. A rabbi should be consulted regarding the use of milk in such areas. This important note is correct and necessary in any case of a person traveling to a strange and new place. He should consult the rabbis or the local Kashrut committees to find out what and who he can rely on.