diff --git a/Signal/translations/en.lproj/Localizable.strings b/Signal/translations/en.lproj/Localizable.strings
index c5d1f86783..ec7be75546 100644
--- a/Signal/translations/en.lproj/Localizable.strings
+++ b/Signal/translations/en.lproj/Localizable.strings
@@ -1624,9 +1624,6 @@
 /* Error indicating that an outgoing message had no valid recipients. */
 "ERROR_DESCRIPTION_NO_VALID_RECIPIENTS" = "Message send failed due to a lack of valid recipients.";
 
-/* Error indicating that a socket request failed. */
-"ERROR_DESCRIPTION_REQUEST_FAILED" = "Network request failed.";
-
 /* Error indicating that a socket request timed out. */
 "ERROR_DESCRIPTION_REQUEST_TIMED_OUT" = "Network request timed out.";
 
@@ -1702,12 +1699,6 @@
 /* Format string for 'unregistered user' error. Embeds {{the unregistered user's name or signal id}}. */
 "ERROR_UNREGISTERED_USER_FORMAT" = "Unregistered User: %@";
 
-/* A default error description. */
-"ERRORS_DEFAULT_ERROR_DESCRIPTION" = "Error";
-
-/* A default error recovery suggestion. */
-"ERRORS_DEFAULT_ERROR_RECOVERY_DESCRIPTION" = "Please try again.";
-
 /* Label notifying the user that the app has expired. */
 "EXPIRATION_ERROR" = "Your version of Signal has expired! Tap to update to the most recent version.";
 
@@ -4555,6 +4546,9 @@
 /* No comment provided by engineer. */
 "REGISTRATION_RESTRICTED_MESSAGE" = "You need to register before you can send a message.";
 
+/* Error message indicating that device transfer from another device might be possible. */
+"REGISTRATION_TRANSFER_AVAILABLE_DESCRIPTION" = "There was an account previously registered with this number that is available for transfer.";
+
 /* Alert view title */
 "REGISTRATION_VERIFICATION_FAILED_TITLE" = "Verification Failed";
 
diff --git a/SignalServiceKit/src/Account/TSAccountManager.swift b/SignalServiceKit/src/Account/TSAccountManager.swift
index da3d55a8e8..72a9fbe94a 100644
--- a/SignalServiceKit/src/Account/TSAccountManager.swift
+++ b/SignalServiceKit/src/Account/TSAccountManager.swift
@@ -278,8 +278,8 @@ extension TSAccountManager {
                                                 comment: "Error message indicating that registration failed due to a missing or incorrect verification code.")
                 failure(OWSErrorWithCodeDescription(.userError, message))
             case 409:
-                // TODO: Localize?
-                let message = "There was an account previously registered with this number that is available for transfer."
+                let message = NSLocalizedString("REGISTRATION_TRANSFER_AVAILABLE_DESCRIPTION",
+                                                comment: "Error message indicating that device transfer from another device might be possible.")
                 failure(OWSErrorWithCodeDescription(.registrationTransferAvailable, message))
             case 413:
                 // In the case of the "rate limiting" error, we want to show the
diff --git a/SignalServiceKit/src/Messages/MessageSender+Errors.swift b/SignalServiceKit/src/Messages/MessageSender+Errors.swift
index 3740bdaa35..9a25378dc9 100644
--- a/SignalServiceKit/src/Messages/MessageSender+Errors.swift
+++ b/SignalServiceKit/src/Messages/MessageSender+Errors.swift
@@ -13,7 +13,6 @@ public enum MessageSenderError: Int, Error, IsRetryableProvider {
     case missingDevice
     case blockedContactRecipient
     case threadMissing
-    // TODO: EncryptionError.missingSession
 
     // MARK: - IsRetryableProvider
 
@@ -122,7 +121,7 @@ public class MessageSenderNoSuchSignalRecipientError: NSObject, CustomNSError, I
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -173,7 +172,7 @@ public class MessageSenderErrorNoValidRecipients: NSObject, CustomNSError, IsRet
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -205,7 +204,7 @@ public class MessageSenderNoSessionForTransientMessageError: NSObject, CustomNSE
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -244,7 +243,7 @@ public class UntrustedIdentityError: NSObject, CustomNSError, IsRetryableProvide
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -289,7 +288,7 @@ public class SignalServiceRateLimitedError: NSObject, CustomNSError, IsRetryable
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -327,7 +326,7 @@ public class SpamChallengeRequiredError: NSObject, CustomNSError, IsRetryablePro
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -369,7 +368,7 @@ public class SpamChallengeResolvedError: NSObject, CustomNSError, IsRetryablePro
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -440,7 +439,7 @@ public class AppExpiredError: NSObject, CustomNSError, IsRetryableProvider {
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -477,7 +476,7 @@ public class AppDeregisteredError: NSObject, CustomNSError, IsRetryableProvider
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -517,7 +516,7 @@ public class MessageDeletedBeforeSentError: NSObject, CustomNSError, IsRetryable
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -544,7 +543,7 @@ public class SenderKeyEphemeralError: NSObject, CustomNSError, IsRetryableProvid
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -579,7 +578,7 @@ public class SenderKeyUnavailableError: NSObject, CustomNSError, IsRetryableProv
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -608,7 +607,7 @@ public class MessageSendUnauthorizedError: NSObject, CustomNSError, IsRetryableP
     /// NSError bridging: the domain of the error.
     /// :nodoc:
     @objc
-    public static let errorDomain = "SignalServiceKit.MessageSender"
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
 
     /// NSError bridging: the error code within the given domain.
     /// :nodoc:
@@ -633,3 +632,34 @@ public class MessageSendUnauthorizedError: NSObject, CustomNSError, IsRetryableP
     // No need to retry if we've been de-authed.
     public var isRetryableProvider: Bool { false }
 }
+
+// MARK: -
+
+@objc
+public class MessageSendEncryptionError: NSObject, CustomNSError, IsRetryableProvider {
+    @objc
+    public let recipientAddress: SignalServiceAddress
+    @objc
+    public let deviceId: Int32
+
+    required init(recipientAddress: SignalServiceAddress, deviceId: Int32) {
+        self.recipientAddress = recipientAddress
+        self.deviceId = deviceId
+    }
+
+    /// NSError bridging: the domain of the error.
+    /// :nodoc:
+    @objc
+    public static let errorDomain = OWSSignalServiceKitErrorDomain
+
+    /// NSError bridging: the error code within the given domain.
+    /// :nodoc:
+    @objc
+    public static var errorCode: Int { OWSErrorCode.messageSendEncryptionFailure.rawValue }
+
+    /// NSError bridging: the error code within the given domain.
+    /// :nodoc:
+    public var errorCode: Int { Self.errorCode }
+
+    public var isRetryableProvider: Bool { true }
+}
diff --git a/SignalServiceKit/src/Messages/MessageSender.swift b/SignalServiceKit/src/Messages/MessageSender.swift
index 330a859cdd..48626f98ba 100644
--- a/SignalServiceKit/src/Messages/MessageSender.swift
+++ b/SignalServiceKit/src/Messages/MessageSender.swift
@@ -1107,10 +1107,6 @@ extension MessageSender {
 }
 
 extension MessageSender {
-    private enum EncryptionError: Error {
-        case missingSession(recipientAddress: SignalServiceAddress, deviceId: Int32)
-    }
-
     @objc(encryptedMessageForMessageSend:deviceId:transaction:error:)
     private func encryptedMessage(for messageSend: OWSMessageSend,
                                   deviceId: Int32,
@@ -1123,7 +1119,7 @@ extension MessageSender {
         guard Self.sessionStore.containsActiveSession(for: recipientAddress,
                                                       deviceId: deviceId,
                                                       transaction: transaction) else {
-            throw EncryptionError.missingSession(recipientAddress: recipientAddress, deviceId: deviceId)
+            throw MessageSendEncryptionError(recipientAddress: recipientAddress, deviceId: deviceId)
         }
         guard let plainText = messageSend.plaintextContent else {
             throw OWSAssertionError("Missing message content")
diff --git a/SignalServiceKit/src/Util/OWSError.h b/SignalServiceKit/src/Util/OWSError.h
index e391ec02b2..0f0481b2db 100644
--- a/SignalServiceKit/src/Util/OWSError.h
+++ b/SignalServiceKit/src/Util/OWSError.h
@@ -9,7 +9,7 @@ NS_ASSUME_NONNULL_BEGIN
 extern NSString *const OWSSignalServiceKitErrorDomain;
 
 // TODO: These error codes are somtimes persisted, so we should
-// explicitly assign a value to every case in this enum.
+//       explicitly assign a value to every case in this enum.
 typedef NS_ENUM(NSInteger, OWSErrorCode) {
     OWSErrorCodeInvalidMethodParameters = 11,
     OWSErrorCodeUnableToProcessServerResponse = 12,
@@ -67,7 +67,8 @@ typedef NS_ENUM(NSInteger, OWSErrorCode) {
     OWSErrorCodeFailedToDecryptDuplicateMessage,
     OWSErrorCodeServerRejectedSuspectedSpam,
     OWSErrorCodeSenderKeyEphemeralFailure,
-    OWSErrorCodeSenderKeyUnavailable
+    OWSErrorCodeSenderKeyUnavailable,
+    OWSErrorCodeMessageSendEncryptionFailure
 };
 
 extern NSError *OWSErrorWithCodeDescription(OWSErrorCode code, NSString *description);
@@ -75,13 +76,5 @@ extern NSError *OWSErrorWithUserInfo(OWSErrorCode code, NSDictionary *userInfo);
 extern NSError *OWSErrorMakeUnableToProcessServerResponseError(void);
 extern NSError *OWSErrorMakeAssertionError(NSString *descriptionFormat, ...);
 extern NSError *OWSErrorMakeGenericError(NSString *descriptionFormat, ...);
-extern NSError *OWSErrorMakeMessageSendDisabledDueToPreKeyUpdateFailuresError(void);
-extern NSError *OWSErrorMakeMessageSendFailedDueToBlockListError(void);
-
-@interface NSError (OWSError)
-
-- (BOOL)ows_isSSKErrorWithCode:(NSUInteger)code;
-
-@end
 
 NS_ASSUME_NONNULL_END
diff --git a/SignalServiceKit/src/Util/OWSError.m b/SignalServiceKit/src/Util/OWSError.m
index 7f0ead307a..4d86f5408f 100644
--- a/SignalServiceKit/src/Util/OWSError.m
+++ b/SignalServiceKit/src/Util/OWSError.m
@@ -48,30 +48,4 @@ NSError *OWSErrorMakeGenericError(NSString *descriptionFormat, ...)
         NSLocalizedString(@"ERROR_DESCRIPTION_UNKNOWN_ERROR", @"Worst case generic error message"));
 }
 
-
-NSError *OWSErrorMakeMessageSendDisabledDueToPreKeyUpdateFailuresError()
-{
-    return OWSErrorWithCodeDescription(OWSErrorCodeMessageSendDisabledDueToPreKeyUpdateFailures,
-        NSLocalizedString(@"ERROR_DESCRIPTION_MESSAGE_SEND_DISABLED_PREKEY_UPDATE_FAILURES",
-            @"Error message indicating that message send is disabled due to prekey update failures"));
-}
-
-NSError *OWSErrorMakeMessageSendFailedDueToBlockListError()
-{
-    return OWSErrorWithCodeDescription(OWSErrorCodeMessageSendFailedToBlockList,
-        NSLocalizedString(@"ERROR_DESCRIPTION_MESSAGE_SEND_FAILED_DUE_TO_BLOCK_LIST",
-            @"Error message indicating that message send failed due to block list"));
-}
-
-@implementation NSError (OWSError)
-
-- (BOOL)ows_isSSKErrorWithCode:(NSUInteger)code
-{
-    BOOL sameDomain = [self.domain isEqualToString:OWSSignalServiceKitErrorDomain];
-    BOOL sameCode = (self.code == code);
-    return (sameDomain && sameCode);
-}
-
-@end
-
 NS_ASSUME_NONNULL_END