The USPTO has encouraged electronic transactions for some time with higher fees for paper filing, but soon, electronic applications for trademark registration may become mandatory. In May, the USPTO proposed changes to the trademark application process. From the announcement:
The proposed changes would generally require trademark applicants and registrants to:
1. File trademark applications and documents concerning trademark applications and registrations online using the USPTO’s Trademark Electronic Application System (TEAS).
2. Provide and maintain an accurate email address for receiving correspondence from the USPTO about a particular application or registration.
This page has detailed information about the proposed changes.