Saying the name of Allaah is a condition of meat being halaal, and it is not excused by forgetting or not knowing, according to the most correct scholarly opinion. See the answer to question no. 85669 (Saying Bismillaah in order to meat to be halaal)?
Meat slaughtered by one of the people of the Book (a Jew or a Christian) is permissible subject to two conditions:
1 – That the meat be slaughtered as a Muslim does it, but cutting the throat and oesophagus and letting the blood flow. If the animal is killed by strangling or electric shock or drowning in water, its meat is not permissible. Similarly, if a Muslim does that, the meat is not permissible.
2 – No name other than that of Allaah should be mentioned over it, such as the name of the Messiah etc, because Allaah says (interpretation of the meaning):
“Eat not (O believers) of that (meat) on which Allaah’s Name has not been pronounced (at the time of the slaughtering of the animal)”
And He says concerning haraam things (interpretation of the meaning):
“He has forbidden you only the Maytah (dead animals), and blood, and the flesh of swine, and that which is slaughtered as a sacrifice for others than Allaah (or has been slaughtered for idols, on which Allaah’s Name has not been mentioned while slaughtering)”
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said:
What is meant here is that over which a name other than that of Allaah is mentioned at the time of slaughter, such as saying “in the name of the Messiah” or “in the name of Muhammad” or “in the name of Jibreel” or “in the name of al-Laat” and so on. End quote from Tafseer Soorat al-Baqarah.
The prohibition also applies to that which is offered as a sacrifice to the Messiah or to al-Zahrah, even if they did not mention a name other than that of Allaah over it. It is also haraam.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said: As for that which is slaughtered by the people of the Book for their festivals and as an act of worship to draw closer to someone other than Allaah, as the Muslims offer their sacrifices to draw closer to Allaah thereby, such as what they slaughter for the Messiah and al-Zahrah, there are two reports narrated from Ahmad concerning that, the most well known of which in his texts is that it is not permissible to eat it, even if the name of someone other than Allaah has not been mentioned over it. The prohibition on doing that was narrated from ‘Aa’ishah and ‘Abd-Allaah ibn ‘Umar. End quote from Iqtida’ al-Siraat al-Mustaqeem (1/251).
If a Muslim or a kitaabi (Jew or Christian) slaughters an animal for meat, and it is not known whether he mentioned the name of Allaah over it or not, it is permissible to eat from it, and the one who eats it should say the name of Allaah, because of the report that was narrated by al-Bukhaari (2057) from ‘Aa’ishah (may Allaah be pleased with her), that some people said: O Messenger of Allaah, some people bring meat to us, and we do not know whether they mentioned the name of Allaah over it or not. The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Mention the name of Allaah over it and eat.”
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: It is not essential to ask about that which was slaughtered by a Muslim or a kitaabi, and how it was slaughtered, and whether the name of Allaah was mentioned over it or not. Rather that should not be done, because that is being obstinate in religious matters. The Prophet (peace and blessings of Allaah be upon him) ate meat slaughtered by the Jews and did not ask questions. In Saheeh al-Bukhaari and elsewhere it is narrated from ‘Aa’ishah (may Allaah be pleased with her) that some people said to the Prophet (peace and blessings of Allaah be upon him): Some people bring meat to us, and we do not know whether they mentioned the name of Allaah over it or not. The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Mention the name of Allaah over it and eat.” She said: They were new in Islam, and the Prophet (peace and blessings of Allaah be upon him) told them to eat without asking, even though those who brought the meat to them may not have been aware of the rulings of Islam because they were new in Islam. End quote from Risaalah fi Ahkaam al-Udhiyah wa’l-Dhakaah by Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him).
Based on the above, whoever travels to a non-Muslim country where most of those who slaughter meat are Christians or Jews, it is permissible for him to eat their meat, unless he knows that they stun the animals or mention over them the name of someone other than Allaah, as stated above.
But if the slaughterman is an idol-worshipper or communist, it is not permissible to eat meat slaughtered by him.
If the meat is haraam, it is not permissible to eat from it on the grounds of necessity, so long as a person can find food to keep him alive, such as fish, vegetables and so on.
Shaykh ‘Abd al-Rahmaan al-Barraak (may Allaah preserve him) said: “The meats available in kaafir countries are of various types. As for fish, it is halaal in all cases, because its being halaal does not depend on the way in which it is slaughtered or on the name of Allaah being mentioned over it.
With regard to other types of meat, if the companies or individuals who produce meat are people of the Book, Jews or Christians, and it is not known from them that they kill the animal by electric shock, strangling or striking it on the head, as is well known in the west, then this meat is halaal. Allaah says (interpretation of the meaning):
“Made lawful to you this day are At‑Tayyibaat [all kinds of Halaal (lawful) foods, which Allaah has made lawful (meat of slaughtered eatable animals, milk products, fats, vegetables and fruits)]. The food (slaughtered cattle, eatable animals) of the people of the Scripture (Jews and Christians) is lawful to you and yours is lawful to them”
But if they kill the animal by one of the methods mentioned, then the meat is haraam, because in that case it is meat that has been strangled or killed by a blow. If those who produce the meat are not Jews or Christians, then the meat that they offer is haraam. Allaah says (interpretation of the meaning):
“Eat not (O believers) of that (meat) on which Allaah’s Name has not been pronounced (at the time of the slaughtering of the animal), for sure it is Fisq (a sin and disobedience of Allaah)”
The Muslim should strive to avoid that which is clearly haraam and be cautious of doubtful matters so as to preserve his religious commitment and to keep his body safe from being nourished with haraam things. End quote.
And Allaah knows best.