Prevent default from email to use a subdomain when the siteurl is a subdomain

[benoitchantre]

When the site url uses a top-level domain or the www subdomain, the default from email is wordpress@mydomain.com

When the site url uses a sub-domain (not www), then the default from email is wordpress@mysubdomain.mydomain.com. In this case, the email will be tagged as spam because the from header domain doesn't the top-level domain.

Would it be possible de force (rewrite) the siteurl variable to remove the subdomain, in order to reduce the chance to have emails marked as spam?

Related: #5007