Fleishig born eggs-Eggs found in a chicken after slaughtering:
While a chicken is alive, it is only permitted to eat eggs that are naturally laid by the chicken after the gestation period is complete. If, however, the egg was removed or knocked out of the live chicken, and was not naturally laid, it is forbidden to eat the egg due to Eiver Min Hachaiy. However, if the egg is found in a slaughtered chicken, then even if the egg is still attached to the sinews of the chicken, the egg remains Kosher. Nonetheless, the Talmud and Poskim state that in certain circumstances, the egg may be considered meaty, and hence forbidden to be eaten with milk. This is dependent on the stage of development that the egg was found in, as will now be explained.
Contains yolk and white: An egg which is found in a slaughtered chicken is permitted to be eaten together with milk if it is fully developed with both a white and yolk. This applies even if the egg is still attached to the sinews. Nonetheless, the custom of the women is to salt such eggs even if it contains a thick shell [and is detached from the sinews], and not to eat it with milk. The above custom is only Lechatchila, however, Bedieved if the egg became mixed with dairy, everything remains Kosher. [Furthermore, communities which do not have the above custom are not to suspect for it at all. The above custom to be stringent not to eat the egg with dairy only applies to eggs found in the chicken after slaughter, and not towards eggs that are naturally laid, even if they have a soft shell and were prematurely laid.]
Contains only yolk: If the egg has not yet fully developed and contains only a yolk without a white, then it is forbidden to cook it or eat it with milk [even if it is not attached to the sinews, and certainly if it is still attached]. Such eggs must be salted for blood prior to being eaten, and may even initially be salted together with meat. However, even in such a case [i.e. only has a yolk and was attached to the sinews], it is permitted to eat milk products after eating the egg. [If these eggs were cooked with milk, some Poskim rule that in a case of great loss one may be lenient to eat the mixture even if it does not contain 60x the egg. This applies even if the egg was still attached to its sinews and only had a yolk, so long as its shell was hard. Other Poskim, however, rule the mixture is forbidden unless it has 60x the egg.]
 See Michaber 87:5; Tur 87:5; Beitza 6b-7a
Background: The Gemara in Beitza ibid states that a developed egg which is found in a chicken may be eaten together with dairy. This implies that an undeveloped egg is considered like meat and may not be eaten together with dairy. The Rishonim and Poskim debate as to the definition of an undeveloped egg, with some holding that even if only the yellow part has been developed the egg is considered pareve, and others holding that so long as the white has not yet developed then it is considered meaty, and others holding that so long as it is still attached to the sinews it is considered like meat. Below we will clarify the final ruling in the different opinions in the Poskim as well as the Jewish custom.
 Michaber Y.D. 86:4; Shach 87:9; Taz 87:6; Kaf Hachaim 87:39; See coming footnotes.
 The egg of a Neveila bird which was killed or naturally died: Eggs found in a dead Neveila chicken are Rabbinically forbidden in consumption. [Michaber 86:3; Shach 86:8]
 Michaber 87:5
 Michaber ibid; Tur 87:5 in name of Rashba; Rashba in Toras Habayis Bayis Gimel Shaar Daled 84b; Rabbeinu Yerucham Nesiv 15:22; Ran Beitza 3b
 If the shell is soft: The Shach 87:10 rules that even if the egg was fully developed and detached from the sinews if the shell is soft, it is initially forbidden to eat the egg with milk. However, Bedieved if it was already cooked with milk it is permitted to eat the mixture in a case of great loss. Although if it was attached to its sinews [and has a soft shell even if fully developed] then even Bedieved it is forbidden. [Shach ibid] Other Poskim, however, argue and rule that in all cases that the egg contains a white and yoke, it is permitted to eat with dairy even if it has a soft shell and is attached to its sinews. [Peri Chadash 87:9]
Small eggs: Small eggs that only have the yolk developed, even if they are not attached to the sinews, are considered like actual meat, although according to the lenient opinion of Rashi, even if only the yolk has developed and the egg is attached one can be lenient Bedieved if it was cooked with milk and there is a great loss.
 Michaber ibid; All Poskim and Rishonim ibid
Why is the egg not considered meaty due to Eiver Min Hachaiy? If an egg was knocked out from a live bird then if it is attached to its sinews it is always forbidden due to Eiver Min Hachaiy, no matter what its stage of development. [Michaber 86:4; Shach 87:9; Taz 87:6] This does not contradict the ruling here that the egg is not considered meat, as Eiver Min Hachaiy applies even by non-meaty parts of the animal. This can be seen from the allowance of milk, that if not for the Torah’s explicit allowance it too would be forbidden due to Eiver Min Hachaiy. Hence although an egg that is attached to its sinews is forbidden due to Eiver Min Hachaiy when it is knocked out of a live chicken, nevertheless this does not mean it is considered meat, and in truth the egg is considered Pareve if it was fully developed. [Shach 87:9] Alternatively it can be explained that only regarding Eiver Min Hachaiy which is Biblical do we view the egg as meat, however regarding the prohibition of meat and milk which is only Rabbinical with chicken, we are not stringent regarding a chicken egg to consider it meat. Or perhaps since each food is permitted on its own we do not consider their mixture to make a new entity of Issur of Basar Bechalav. Nevertheless, the above explanations are unnecessary, as in truth, the egg is not considered meat at all. [Shach ibid]
Opinion of Rashal: The Rashal [brought in Taz 87:6] however rules that all eggs which are attached to their sinews are considered meat for all matters. His reasoning is because we see from the law of Eiver Min Hachaiy, that when an egg gets pushed out from a chicken when it was still attached to its sinews that it is Treif. One must say, says the Rashal, that the reason for this is because the egg is considered meat so long as it is still attached. Hence, so too here the egg is considered meat even when fully developed if it is still attached to the sinews.
 It is initially to be salted by itself, without meat. [Rama 75:1; Kaf Hachaim 87:40]
 Rama 75:1; Taz 87:6; Shach 87:10; Toras Chatas Klal 70:1 in name of Mahariy; Darkei Moshe 87:3; Rashal Kol Habasar 2; Bach 87; Beis Hillel 87:4; Lechem Hapanim 87:10; Beis Lechem Yehuda 87:7; Chochmas Adam 40:5; Beis Yitzchak 87:5; Kaf Hachaim 87:37
Background of the custom of women to forbid all eggs: The Mahariy [brought in Rashal and Shach 87:10] rules that the women are accustomed to being stringent to avoid eating eggs found in slaughtered chickens even if the shell is hard [and it is detached from the sinews]. The Rashal concludes that Bedieved one is not to be stringent if the shell has completed, even if it is soft. [Taz 87:6] The Shach [87:10] likewise brings this custom of women and concludes it is a mere stringency and in an area where this custom was not accepted they do not need to follow it [even if the egg is attached to the sinews] as when the outer shell is hard, it is permitted even initially to eat it with milk.
 Rama ibid; Taz ibid; Shach ibid; Toras Chatas ibid; Beis Hillel ibid; Chochmas Adam ibid; Beis Yitzchak ibid; Kaf Hachaim 87:38
 Shach ibid; Lechem Hapanim ibid; Kaf Hachaim 87:38
 Sheilas Yaavetz 1:102; Pischeiy Teshuvah 87:12
 Michaber ibid; Tur 87; Rashba in Toras Habayis Bayis Gimel Shaar Daled 84b; Rabbeinu Yerucham Nesiv 15:22; Ran Beitza 3b
Other opinions: Some Poskim rule that even if the egg has only developed the yolk and not the white, and is found attached to the sinews, it is considered Pareve and may be eaten with dairy. [Tur 87 in name of Rashi; Rashi Beitza 6b; Tosafus Beitza 7a; Rosh 1:8; Rabbeinu Yerucham Nesiv 15:28; Brought in Shach 87:12]
 Michaber writes cook, Shach [87:11] writes he means “eat” as even chicken itself the Michaber rules may be cooked with milk. [However, just as cooking chicken with milk is forbidden due to Maaras Ayin, so too the same would apply to this form of egg.]
 Shach 87:10; Peri Chadash 87:9
 Rama 75:1
 Shach 87:12; Peri Chadash 87:10; Peri Tora 87:13; Lechem Hapanim 87:11; Beis Lechem Yehuda 87:9
 Michaber ibid; Orchos Chaim Issuei Machalos 72 in name of Rav Yonason of Lunil
Other opinions: Some Poskim rule one is to be stringent and not eat dairy within six hours of eating such eggs, just as is followed regarding poultry. [Peri Chadash 87:10; Peri Tora 87:13; Lechem Hapanim 87:11; Beis Lechem Yehuda 87:9; Zivcheiy Tzedek 87:32; Kaf Hachaim 87:42]
 Shach 87:10; Beir Heiytiv 87:8; Based on ruling of: Tur 87 in name of Rashi; Rashi Beitza 6b; Tosafus Beitza 7a; Rosh 1:8; Rabbeinu Yerucham Nesiv 15:28; Brought in Shach 87:12
 Peri Chadash 87:9; Zivcheiy Tzedek 87:31; Kaf Hachaim 87:41