We have some roles that people can choose regarding how they want to engage with people privately.
DM Anytime: Someone who has this role will have no issue with you sending them an unprompted direct message.
Ask to DM: This person expects you to @tag them in an open channel and request to be able to send them a direct message. You must not contact them privately until they have given you permission to do so.
Never DM: This person does not wish to receive private messages and does not wish to be asked if you can DM them. You may not do either of these things. If the member has not selected any roles, treat them as if they selected the Ask to DM role.
Contacting someone privately without their consent is a breach of house protocol and if discovered, will result in a BAN, no warnings. This includes sending friend requests.