Regards used with Regarding

Greetings,

I am having a debate at work. I say it is not incorrect grammar in this sentence.

In Regards to the email you sent us 5/30/18. Regarding the weather.

I say it is not bad grammar because they are in two different sentences and they are different words. My coworker says it is redundant using a form of regarding twice thus bad grammar.

I advised Regards and regarding are complimentary words.