A consent should show what the person deliberately accepted and how. Spain’s AEPD, in its report 0011/2014 on pixels in advertising emails, said that a link to a privacy policy plus the absence of an objection is not enough.
For each tracking consent HawkOpen stores the source, the date, the purpose and the version of the information shown. Ask a qualified specialist for marketing wording that fits your country and purpose.
Where rules that require consent apply, tracking may start only after that consent has been obtained. The link in the message lets the recipient withdraw consent later.