About This HTML Issue
This mailto: link has a space somewhere in its address, and a URL can't contain a raw space.
The validator says the space comes "after ilto:", which means anywhere after the scheme, not only right after the colon. It flags a space typed after mailto:, a space inside the address, a space after the comma between two recipients, and text or markup left in the attribute after the address, such as mailto:info@example.com <br>. That last case shows up when a template or CMS field drops HTML into the link.
A mailto: URL, defined in RFC 6068, holds one or more bare email addresses after the colon. Some browsers open the mail client anyway, but the extra text can end up in the recipient field.
A space inside the subject or body parameters triggers a different message, "Illegal character in query". Encode those spaces as %20.
To fix it, remove the spaces and anything after the address that isn't part of it. Separate several recipients with a comma and no space.
Invalid example
<a href="mailto: info@example.com">Email us</a>
<a href="mailto:info@example.com, sales@example.com">Email us</a>
<a href="mailto:info@example.com <br>">Email us</a>
Valid example
<a href="mailto:info@example.com">Email us</a>
<a href="mailto:info@example.com,sales@example.com">Email us</a>
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