Solicitation of SSN

[Chaz]

In order to comply with the 6055 and 6056 reporting requirements, certain employers/plans must generally make reasonable efforts to obtain the social security number or TIN of participating spouses and dependents.

In order to properly solicit this information, can an employer/plan send an e-mail request (in accordance with the ERISA electronic notification rules) or must it send the solicitation via snail mail (except for those who affirmatively consent to electronic delivery)?

Thanks.