S.D. Codified Laws § 55-19-4
Any user may utilize an online tool to direct a custodian to disclose or not to disclose to a designated recipient some or all of the user's digital assets, including the content of electronic communications. If the online tool allows the user to modify or delete a direction at all times, a direction regarding disclosure using an online tool overrides a contrary direction by the user in a will, trust, power of attorney, or other record.
If a user has not utilized an online tool to give direction under this section, or if the custodian has not provided an online tool, the user may allow for or prohibit in a will, trust, power of attorney, or any other record, disclosure to a fiduciary of some or all of the user's digital assets, including the content of electronic communications sent or received by the user.
A user's direction under this section overrides a contrary provision in any terms-of-service agreement that does not require the user to act affirmatively and distinctly from the user's assent to the terms of service agreement.
SDCL 55-19-4