Invalid ContactPerson element in SAML metadata will result in a "OpenSAML.MetadataProvider.XML : metadata instance failed manual validation checking: EmailAddress must have TextContent." error message loading the metadata. The same message can occur for PhoneNumber element.
Requirement for ContactPerson element in SAML metadata
It is not a requirement of the SAML specification that you include the <ContactPerson> element, or it's sub-elements, in your SSO metadata at all. However, it is a requirement of the specification (section 1.3.2) that if you do include these elements they cannot be empty. We are not able to process invalid SAML metadata, and manual modifications to the metadata would invalidate any signatures on the metadata.
ADFS values for contact person
ADFS will emit (invalid) SAML metadata if the E-mail address and Telephone number fields are left blank in the Federation Service Properties. Please note, these values are global for your metadata, and not specific to any one relying party.
The screen shot below shows where/how to edit this information. Only the items in step 3 and 4 must be provided, and there is no restriction on what you place there so long as you place something there -- though it is a convenient place to store relevant contact information.
Please note, the values shown below are from our ADFS instance, your values will differ and should reflect your contact information.