Twenty-eight states offer "no-excuse" absentee voting, which means that any voter can request and cast an absentee/mail ballot, no excuse or reason necessary.
Eight states and Washington, D.C., conduct elections entirely by mail (California, Colorado, Hawaii, Nevada, Oregon, Utah, Vermont and Washington), which means voters do not need to request a ballot, and instead automatically receive one.
The remaining states require a voter to provide an excuse to qualify for an absentee/mail ballot. See Table 2: Excuses to Vote Absentee for details.