The bug

Certain projectiles, when thrown or launched at an Enderman, will not cause it to teleport away, or will hit/interact with the Enderman even though it teleported.

The following projectiles hit the Enderman, and the Enderman will not attempt to teleport:

• Anvils or other Falling Blocks
• Dragon Fireball
• Lingering Potions (excluding Lingering Water Bottles)
• Firework Rockets (explosive or non-explosive)
  • Can be hand-placed or fired from Crossbows or Dispensers
  • Can be direct hits or indirect splash damage
  • Tracked but marked as Fixed at MC-144928
• Non-damaging Splash Potions
• Splash Potions of Poison
• Other non-damaging projectiles such as Bottles o’ Enchanting or a Fishing Bobber
  • Fishing Bobbers attaching to Endermen tracked at MC-96092

The following will hit, damage, or be destroyed upon contact, and the Enderman will teleport:

• Black and Blue Wither Skull projectiles
  • Projectile is destroyed
  • Projectile applies the Wither effect as the Enderman teleports away
    • Wither Skull projectiles applying the Wither effect to Endermen tracked at MC-186119
  • Enderman doesn't appear to take impact damage; only effect damage and, if the skull hits nearby, splash damage
• Blaze Fireballs and Fire Charges fired from a Dispenser
  • Projectile is destroyed
  • Enderman will be set aflame
• Ghast Fireball
  • Fireball explodes
  • Enderman only takes damage if it hits something nearby instead of a direct hit
• Eggs, Ender Pearls, Snowballs
  • Projectile is destroyed
  • Enderman teleports without taking damage
• Shulker Bullet
  • Projectile is destroyed
  • The Enderman does not take damage, but still receives the Levitation effect
    • Shulker Bullets applying Levitation to Endermen tracked at MC-234625
• Splash Potion of Harming
  • Potion is destroyed
  • Enderman dodges and is unharmed from both direct and indirect hits
• Splash Water Bottle and Lingering Water Bottle
  • Enderman takes damage from direct and indirect hits, but still teleports
  • The knockback they receive is not removed, causing the Enderman to appear to jump when it teleports and causing it to land around a block away from its teleport location
• Trident (With Loyalty)
  • Trident will usually immediately start slowing down and will return to the thrower
  • Enderman is unharmed
• Wind Charge
  • Wind Charge explodes, and the Enderman teleports and is unaffected
  • If it hits nearby, the Enderman does not teleport and is knocked back from the blast

The following will be successfully avoided by the Enderman, and the projectile will continue in its trajectory:

• Arrows (any type) fired from a Bow, Crossbow, or Dispenser
  • If a group of Endermen are too close together, shooting an Arrow will only make one or two of them teleport, and the arrow will pass through the rest harmlessly
• Trident (Without Loyalty)
  • Arrows and Tridents may appear to wobble or shake when coming in contact with an Enderman. This doesn't seem to change their location or momentum, but will change the direction they're facing temporarily before reverting
    • In 1.21.2+, arrows/tridents that pass through an Endermen may pause/stall for a tick upon collision, before continuing on their path
  • Endermen will not try to avoid a Trident that has already passed through another Enderman, or one that has hit a block
    • Likely due to MC-130151 and MC-271283; Tridents unable to interact with / deal damage to entities after impacting something or passing through an Enderman
• Llama spit

Other notes:

• If an Enderman fails to pick a new place to teleport to, the projectile may just bounce off.