What is Delta Fare Class E?
Delta Fare Class E or more commonly known as Basic (E) is a revenue fare/booking class of service on Delta Air Lines. The E fare class is the lowest (least expensive) fare class in the Basic Economy Cabin and tickets are the most restrictive. This fare class is not eligible for complimentary upgrades and earns no SkyMiles.
Below is a human-readable explanation of this fare class and the expectations passengers should have when flying with a E fare class.

Fare Class E booking information
Important information about Fare Class E on Delta Air Lines.
Fare Class E is marketed as a basic economy ticket, and is the lowest fare class with the most restrictions. If you’re looking for flights and see Fare Class E showing as the lowest fare class available, it means the flight/route you are booking is nearly empty with only few seats purchased.
Tickets purchased in Fare Class E will be the cheapest. You may find Main Cabin fare classes available for purchase for a similar price.

SkyMiles frequent flyer earnings
Explore what you’ll earn as a SkyMiles member flying on Delta Air Lines with a ticket in Fare Class E.
SkyMiles medallion members will not earn any MQM, MQS, MQD and SkyMiles when flying on a Basic Economy (Fare Class E) ticket. Additionally, Basic Economy boards the plane last which will likely result in a gate-checking a bag that does not fit under your seat.
For SkyMiles members who want to earn SkyMiles and/or status, DO NOT book Basic Economy tickets.
For non-SkyMiles members who do not intend to build loyalty with Delta Air Lines, there’s no significant reason not to book Basic Economy.

SkyMiles upgrades with Fare Class E ticket
Important upgrade eligibility and upgrade order information with a Fare Class E ticket on Delta Air Lines.
Complimentary upgrades are not available for SkyMiles Medallions at any tier (even Diamonds and 360’s). In addition, advanced seat selection not available as will be assigned at the gate shortly before boarding.