You may opt out of receiving promotional communications from Couchsurfing by following the instructions in those emails or by adjusting the appropriate settings in your profile. If you opt out, we may still send you transactional or relationship messages, such as emails about your account.</p>

"You may opt out of receiving promotional emails from CouchSurfing by following the instructions in those emails or by adjusting the appropriate settings in your profile." - this means the default is that they will send you promotional communications that you didn't ask them to send you.