diff --git a/Sources/SuperwallKit/Identity/Email.swift b/Sources/SuperwallKit/Identity/Email.swift
new file mode 100644
index 0000000000..2e915fbef6
--- /dev/null
+++ b/Sources/SuperwallKit/Identity/Email.swift
@@ -0,0 +1,29 @@
+//
+//  Email.swift
+//  SuperwallKit
+//
+
+import Foundation
+
+/// A validated email address.
+///
+/// The failable initializer rejects any string that does not match the
+/// pattern expected by the checkout API (`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`).
+/// Holding an `Email` instance proves the value was validated — downstream
+/// code never needs to re-check.
+struct Email: Equatable, Sendable {
+  let rawValue: String
+
+  private static let regex = try! NSRegularExpression(
+    pattern: #"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"#
+  )
+
+  /// Returns `nil` when `rawValue` is not a syntactically valid email address.
+  init?(_ rawValue: String) {
+    let range = NSRange(rawValue.startIndex..., in: rawValue)
+    guard Self.regex.firstMatch(in: rawValue, range: range) != nil else {
+      return nil
+    }
+    self.rawValue = rawValue
+  }
+}
diff --git a/Sources/SuperwallKit/Identity/UserAttributes.swift b/Sources/SuperwallKit/Identity/UserAttributes.swift
index f3e390c4ac..6ff8d8e2a3 100644
--- a/Sources/SuperwallKit/Identity/UserAttributes.swift
+++ b/Sources/SuperwallKit/Identity/UserAttributes.swift
@@ -94,11 +94,39 @@ extension Superwall {
           continue
         }
         if JSONSerialization.isValidJSONObject([key: value]) {
-          customAttributes[key] = value
+          customAttributes[key] = Self.sanitizeAttribute(key: key, value: value)
         }
       }
     }
 
     dependencyContainer.identityManager.mergeUserAttributes(customAttributes)
   }
+
+  /// Validates attribute values that have server-side schema constraints.
+  ///
+  /// The checkout API rejects `context.identity.email` unless it is either a
+  /// valid email address or `null`. Apps that set a placeholder like `"none"`
+  /// would silently break the Stripe checkout flow, so the SDK parses the
+  /// value through ``Email`` and drops it when invalid.
+  static func sanitizeAttribute(key: String, value: Any?) -> Any? {
+    guard let stringValue = value as? String else {
+      return value
+    }
+
+    switch key {
+    case "email":
+      guard let email = Email(stringValue) else {
+        Logger.debug(
+          logLevel: .warn,
+          scope: .identityManager,
+          message: "Invalid email user attribute \"\(stringValue)\" — sending null to server"
+        )
+        return nil
+      }
+      return email.rawValue
+
+    default:
+      return value
+    }
+  }
 }
diff --git a/Tests/SuperwallKitTests/Identity/EmailTests.swift b/Tests/SuperwallKitTests/Identity/EmailTests.swift
new file mode 100644
index 0000000000..35c9444614
--- /dev/null
+++ b/Tests/SuperwallKitTests/Identity/EmailTests.swift
@@ -0,0 +1,131 @@
+//
+//  EmailTests.swift
+//  SuperwallKit
+//
+
+import Testing
+@testable import SuperwallKit
+
+@Suite("Email")
+struct EmailTests {
+
+  // MARK: - Valid emails
+
+  @Test("accepts a simple email address")
+  func `simple email`() {
+    #expect(Email("user@example.com") != nil)
+  }
+
+  @Test("accepts email with dots in local part")
+  func `dotted local part`() {
+    #expect(Email("first.last@domain.co") != nil)
+  }
+
+  @Test("accepts email with plus tag")
+  func `plus tag`() {
+    #expect(Email("user+tag@example.com") != nil)
+  }
+
+  @Test("accepts email with subdomain")
+  func `subdomain`() {
+    #expect(Email("user@mail.example.co.uk") != nil)
+  }
+
+  @Test("accepts email with numbers")
+  func `numbers`() {
+    #expect(Email("user123@domain456.com") != nil)
+  }
+
+  @Test("accepts email with hyphen in domain")
+  func `hyphenated domain`() {
+    #expect(Email("user@my-domain.com") != nil)
+  }
+
+  @Test("accepts email with underscore and percent")
+  func `underscore and percent`() {
+    #expect(Email("user_%name@domain.org") != nil)
+  }
+
+  @Test("preserves the raw value on success")
+  func `preserves raw value`() {
+    let address = "hello@world.com"
+    let email = Email(address)
+    #expect(email?.rawValue == address)
+  }
+
+  // MARK: - Invalid emails
+
+  @Test(
+    "rejects strings that are not valid email addresses",
+    arguments: [
+      "none",
+      "",
+      "userexample.com",
+      "user@",
+      "@example.com",
+      "user@domain",
+      "user@domain.a",
+      "user @example.com",
+      "not an email",
+      "null",
+      "N/A",
+    ]
+  )
+  func `rejects invalid value`(value: String) {
+    #expect(Email(value) == nil)
+  }
+
+  // MARK: - Equatable
+
+  @Test("two emails with the same address are equal")
+  func `equal emails`() {
+    #expect(Email("a@b.com") == Email("a@b.com"))
+  }
+
+  @Test("two emails with different addresses are not equal")
+  func `different emails`() {
+    #expect(Email("a@b.com") != Email("x@y.com"))
+  }
+}
+
+// MARK: - sanitizeAttribute
+
+@Suite("Superwall.sanitizeAttribute")
+struct SanitizeAttributeTests {
+
+  @Test("passes a valid email through unchanged")
+  func `valid email passes through`() {
+    let result = Superwall.sanitizeAttribute(key: "email", value: "user@example.com")
+    #expect(result as? String == "user@example.com")
+  }
+
+  @Test("replaces the placeholder 'none' with nil for the email key")
+  func `none placeholder becomes nil`() {
+    let result = Superwall.sanitizeAttribute(key: "email", value: "none")
+    #expect(result == nil)
+  }
+
+  @Test("replaces an empty string with nil for the email key")
+  func `empty string becomes nil`() {
+    let result = Superwall.sanitizeAttribute(key: "email", value: "")
+    #expect(result == nil)
+  }
+
+  @Test("does not sanitize non-email keys")
+  func `non email key untouched`() {
+    let result = Superwall.sanitizeAttribute(key: "name", value: "none")
+    #expect(result as? String == "none")
+  }
+
+  @Test("does not sanitize non-string values on the email key")
+  func `non string value untouched`() {
+    let result = Superwall.sanitizeAttribute(key: "email", value: 42)
+    #expect(result as? Int == 42)
+  }
+
+  @Test("passes nil through unchanged")
+  func `nil value passes through`() {
+    let result = Superwall.sanitizeAttribute(key: "email", value: nil)
+    #expect(result == nil)
+  }
+}