What are the consequences of having a marriage with a non-Mormon or outside the temple?
A marriage between a Mormon and a non-Mormon is like any other marriage solemnized under the authority of the State. That marriage, whether performed by a civil authority or an ecclesiastical authority, including a bishop in the Mormon Church, is authorized only for the mortal duration. The officiating authority will utter some phrase such as “until death do you part” or “for the duration of your mortal lives.” Such contracts are binding only until the death of one of the partners. The contract has then been fulfilled, and the marriage at that point is null and void. No such ecclesiastical or civil authority has any power to bind any contract that may be stated or inferred to be carried over into a post-mortal life. So these marriages may be said to contain from the outset a built-in divorce.
Any marriage between two members of the Mormon Church that is performed outside the temple must be performed by a bishop of the Mormon church or by some civil authority and is, of course, the same as explained under item 1.
To have a marriage performed in the temple, the contracting parties must be members of the Mormon Church, and must be living pure lives in full accord with all the principles of the gospel. Such marriages are solemnized by officiators who have received from the President of the Mormon Church the authority “to seal on earth and it shall be sealed in heaven.” Associated with those marriages are sacred covenants of continued obedience to all the principles of the gospel made between the contracting parties and the Lord himself. If the contracting parties are true to the covenants thus entered into, they will be raised from the dead in the morning of the first resurrection and will inherit the glory of exaltation in the Celestial Kingdom, which represents the greatest and highest blessing that our Father in Heaven has prepared to give to any of his children as they pass from mortality into eternity.