Yeah, as @Justin_Barrett said, if you want to do this entirely via email, I think the quickest/easiest way of doing this would be to just use Integromat to parse the emails on your behalf — but you’d have to “encode” the outgoing emails to the clients in some way that you would know what question the person is replying to, and you’d need to know which person is doing the replying. (You’d also need to make sure that the person doesn’t alter the parts of the email which you’ve encoded.)
So, for example, you could put the Record ID of the question within the subject of the email. Then, when the person replies to the email, Integromat can parse the subject of the email to figure out which question the person is replying to. Then, Integromat can grab the person’s email address, and do a search for that person by their email address in Airtable.
And then Integromat can link that person to the question + their reply in Airtable.
You could also setup scenarios for what to do if the Record ID is missing or the person’s email address doesn’t exist in your Airtable base.
Also, Integromat offers mailhooks, so the “Reply To” email address on your outgoing emails could be the Integromat email address, meaning that replies will get sent directly into Integromat — without any need for a normal email address to be monitored by Integromat.
p.s. I am a professional Airtable consultant and an Integromat Partner, and the Integromat links contain my personal referral code. If you have a budget for your project and you’d like to hire an expert to help you set this up, please feel free to contact me through my website at ScottWorld.com.