I have a subdomain crm(dot)mydomain(dot)com which is hosted on separate server than my main domain - mydomain(dot).com and linked to it through A records.

I would like to be able to send emails from this subdomain as if they were coming from the main domain, so for example info(at)mydomain(dot)com and not info(at)crm(dot)mydomain(dot)com

I did set up and validated SPF for mydomain(dot).com and also crm(dot)mydomain(dot).com and they emails from both successfully passe the spf verifications for outgoing emails. However I have a very hard time setting up DIKM for crm(dot)mydomain(dot).com as I cannot create a DKIM key in zoho for the subdomain, i.e. somekey(dot)_domainkey(dot)crm(dot)mydomain(dot)com as Zoho only allows me to create DKIM for the main domain somekey(dot)_domainkey(dot)mydomain(dot)com. Since I can only create DKIM record for the main domain I cannot DKIM validate emails going from my subdomain.

Could you please advise on how to do it correctly, so my outgoing emails from crm(dot)mydomain(dot)com pass DKIM validation? Thank you in advance for your help.