TRCP Rule 21a. (a) (1)

1. Documents Filed Electronically. A document filed electronically under Rule 21 must be served electronically through the electronic filing manager if the email address of the party or attorney to be served is on file with the electronic filing manager. If the email address of the party or attorney to be served is not on file with the electronic filing manager, the document may be served on that party or attorney under subparagraph (2).
2. Documents Not Filed Electronically. A document not filed electronically may be served in person, by mail, by commercial delivery service, by fax, by email, or by such other manner as the court in its discretion may direct.