Validating email addresses is hard

These are all valid email addresses!

• Abc@def@example.com
• Fred\ Bloggs@example.com
• Joe.\Blow@example.com
• “Abc@def”@example.com
• “Fred Bloggs”@example.com
• customer/department=shipping@example.com
• $A12345@example.com
• !def!xyz%abc@example.com
• _somename@example.com

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