Scales to Play Over E7
Every chord is a subset of several scales: any scale that contains all of a chord's tones fits over it. Pick a chord to see the matching scales from its own root, the major keys the chord belongs to, and full fretboard diagrams for every scale on guitar.
A E7 chord contains the notes E – G# – B – D. Any scale that includes every one of those 4 tones fits over it — from the root E, that means E Mixolydian, E Dorian Bebop, E Mixolydian Bebop, E Half Whole Diminished, E Spanish and E Gypsy Major. Start with the first scale listed: it is the most common choice, and the others color the same chord tones differently.
E7 is also diatonic to one major key: A major (relative minor F#m). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.