As a general guideline, whom is considered rather formal, so sentence 1 is fine in a formal setting. In spoken English we like to put the preposition at the end, but whom is really too formal here. Better...
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GuyperSo, what you are saying is that whenever we use whom, the preposition must always be placed before it and never at the end, is that right?Basically, yes. Some American speakers might disagree, but it's all a question of register
"With whom can I speak?"
"Who can I speak with?"
Are these two sentences correct? Thanks