if you enable DKIM for a domain, can you send using mail servers which do not use DKIM?

Question

I have two mail servers which we use to send emails - One of them is through Mandrill to send transactional emails from a website. Mandrill supports DKIM and we have enabled it and also set the required TXT records.

We also use an inhouse mail server in the office to send as well emails, and this one does not support DKIM. Will this create a problem for emails sent from office appearing as not authenticated or spam?

Answer 1

It shouldn't be a problem. Having the DKIM signature on your messages is a 'plus' as far as indicating to spam filters and other mail servers that these messages are valid messages. But, not having the DKIM signature would not be considered a 'strike'.