How to respond to an employer after refusing the resignation?

I am working now as a Data Entry Clerk/Medical Transcriptionist in Dubai in a free zone company for more than 2 years under an unlimited contract.

I finished the contract of 2 years (limited contract) and renewed for another year in which it became unlimited. I sent my resignation in July 2019 with a notice period of 1 month, but my employer rejected it.

On 24 October 2019, I sent my resignation again, and he rejected it again saying that he did not receive the letter and accidentally saw it when he came, as he is out of the country.

I am sending my resignation through email as my employer is not usually coming to the office and it is impossible for him not to receive it as my second resignation was twice and the PRO confirmed that he received it as I put him in CC.

What should I do? And how can I respond to my employer?