One of our client's mail-server at   ..... @valvo.com.mx is rejecting our emails from sendgrid with the response of ''541 5.4.1 Mail rejected by destination domain'. Our domains at 'archdaily.com' and 'api.archdaily.com' are not sending him newsletters or spam but actually leads, quote requests and info from users through a form. 

Here are some screenshots of the client already having to go through the whitelists with our emails: 

I've seen some posts here that get this issue fixed for their email domains, can you help us as well in this case? These are transactional emails with leads, so it is a big issue for the client. THis also might affect other clients that use zoho email,  so it's even more important.