Position of Adverbs of manner

Hello,

Are only adverbs of manner allowed to follow immediately after verbs? Alternatively, adverbs of manner can always precede immediately before verbs, can't they?

The following sentences are examples:

Sentence A. He spoke gently to the audience.

Sentence B. He gently spoke to the audience.

I do not understand why the positions of the adverbs of manner in the following make the sentences seem ungrammatic. Could you explain them, please?

Sentence C. He addressed gently his remarks to his audience.

Sentence D. He addressed his remarks gently to his audience.

Sentence E. He addressed his audience gently.

Sentence F. He addressed gently his audience.

Thank you.

With best wishes.