49 CFR §105.35

1. (a)Service by PHMSA. We may serve the document by one of the following methods, except where a different method of service is specifically required:
   1. (1)Registered or certified mail.
      1. (i)If we serve a document by registered or certified mail, it is considered served when mailed.
      2. (ii)An official United States Postal Service receipt from the registered or certified mailing is proof of service.
      3. (iii)We may serve a person's authorized representative or agent by registered or certified mail, or in any other manner authorized by law. Service on a person's authorized agent is the same as service on the person.
   2. (2)Personal service.
   3. (3)Publication in the Federal Register.
   4. (4)Electronic service.
      1. (i)Service by electronic means if consented to in writing by the party to be served.
      2. (ii)For all special permits and approvals actions, electronic service is authorized.
2. (b)Service by others. If you are required under this subchapter to serve a person with a document, serve the document by one of the following methods, except where a different method of service is specifically required:
   1. (1)Registered or certified mail.
      1. (i)If you serve a document by registered or certified mail, it is considered served when mailed.
      2. (ii)An official United States Postal Service receipt from the registered or certified mailing is proof of service.
      3. (iii)You may serve a person's authorized representative or agent by registered or certified mail or in any other manner authorized by law. Service on a person's authorized agent is the same as service on the person.
   2. (2)Personal service.
   3. (3)Electronic service.
      1. (i)In a proceeding under § 107.317 of this subchapter (an administrative law judge proceeding), you may electronically serve documents on us.
      2. (ii)Serve documents electronically through the Internet at http://www.regulations.gov.