diff --git a/SoObjects/Mailer/SOGoMailAccount.h b/SoObjects/Mailer/SOGoMailAccount.h
index 66da6f06d..daf9a859f 100644
--- a/SoObjects/Mailer/SOGoMailAccount.h
+++ b/SoObjects/Mailer/SOGoMailAccount.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2009-2017 Inverse inc.
+  Copyright (C) 2009-2019 Inverse inc.
 
   This file is part of SOGo.
 
@@ -34,6 +34,7 @@
 */
 
 @class NSArray;
+@class NSException;
 @class NSMutableDictionary;
 @class NSMutableArray;
 @class NSString;
@@ -79,11 +80,11 @@ typedef enum {
 - (BOOL) supportsQResync;
 
 - (id) getInboxQuota;
-- (BOOL) updateFilters;
-- (BOOL) updateFiltersAndForceActivation: (BOOL) forceActivation;
-- (BOOL) updateFiltersWithUsername: (NSString *) theUsername
-                       andPassword: (NSString *) thePassword
-                   forceActivation: (BOOL) forceActivation;
+- (NSException *) updateFilters;
+- (NSException *) updateFiltersAndForceActivation: (BOOL) forceActivation;
+- (NSException *) updateFiltersWithUsername: (NSString *) theUsername
+                                andPassword: (NSString *) thePassword
+                            forceActivation: (BOOL) forceActivation;
 
 - (NSArray *) identities;
 - (NSString *) signature;
diff --git a/SoObjects/Mailer/SOGoMailAccount.m b/SoObjects/Mailer/SOGoMailAccount.m
index e58539a13..38bb20458 100644
--- a/SoObjects/Mailer/SOGoMailAccount.m
+++ b/SoObjects/Mailer/SOGoMailAccount.m
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2007-2016 Inverse inc.
+  Copyright (C) 2007-2019 Inverse inc.
 
   This file is part of SOGo.
 
@@ -300,21 +300,21 @@ static NSString *inboxFolderName = @"INBOX";
   return inboxQuota;
 }
 
-- (BOOL) updateFiltersAndForceActivation: (BOOL) forceActivation
+- (NSException *) updateFiltersAndForceActivation: (BOOL) forceActivation
 {
   return [self updateFiltersWithUsername: nil
                              andPassword: nil
                          forceActivation: forceActivation];
 }
 
-- (BOOL) updateFilters
+- (NSException *) updateFilters
 {
   return [self updateFiltersWithUsername: nil
                              andPassword: nil
                          forceActivation: NO];
 }
 
-- (BOOL) updateFiltersWithUsername: (NSString *) theUsername
+- (NSException *) updateFiltersWithUsername: (NSString *) theUsername
                        andPassword: (NSString *) thePassword
                    forceActivation: (BOOL) forceActivation
 {
diff --git a/SoObjects/SOGo/SOGoSieveManager.h b/SoObjects/SOGo/SOGoSieveManager.h
index 0a179dc65..add00f801 100644
--- a/SoObjects/SOGo/SOGoSieveManager.h
+++ b/SoObjects/SOGo/SOGoSieveManager.h
@@ -25,6 +25,7 @@
 
 
 @class NSDictionary;
+@class NSException;
 @class NSMutableArray;
 @class NSString;
 @class NGSieveClient;
@@ -52,8 +53,8 @@
 
 - (BOOL) hasActiveExternalSieveScripts: (NGSieveClient *) client;
 
-- (BOOL) updateFiltersForAccount: (SOGoMailAccount *) theAccount;
-- (BOOL) updateFiltersForAccount: (SOGoMailAccount *) theAccount
+- (NSException *) updateFiltersForAccount: (SOGoMailAccount *) theAccount;
+- (NSException *) updateFiltersForAccount: (SOGoMailAccount *) theAccount
                     withUsername: (NSString *) theUsername
                      andPassword: (NSString *) thePassword
                  forceActivation: (BOOL) forceActivation;
diff --git a/SoObjects/SOGo/SOGoSieveManager.m b/SoObjects/SOGo/SOGoSieveManager.m
index bbc6366af..f315426fa 100644
--- a/SoObjects/SOGo/SOGoSieveManager.m
+++ b/SoObjects/SOGo/SOGoSieveManager.m
@@ -37,6 +37,7 @@
 #import <NGImap4/NGImap4Connection.h>
 #import <NGImap4/NGImap4Client.h>
 #import <NGImap4/NGSieveClient.h>
+#import <NGObjWeb/NSException+HTTP.h>
 
 #import "../Mailer/SOGoMailAccount.h"
 
@@ -816,7 +817,7 @@ static NSString *sieveScriptName = @"sogo";
   while ((key = [keys nextObject]))
     {
       if ([key caseInsensitiveCompare: @"sogo"] != NSOrderedSame &&
-          [[[scripts objectForKey: key] stringValue] length] > 0)
+          [[scripts objectForKey: key] intValue] > 0)
         return YES;
     }
 
@@ -826,7 +827,7 @@ static NSString *sieveScriptName = @"sogo";
 //
 //
 //
-- (BOOL) updateFiltersForAccount: (SOGoMailAccount *) theAccount
+- (NSException *) updateFiltersForAccount: (SOGoMailAccount *) theAccount
 {
   return [self updateFiltersForAccount: theAccount
                           withUsername: nil
@@ -837,15 +838,16 @@ static NSString *sieveScriptName = @"sogo";
 //
 //
 //
-- (BOOL) updateFiltersForAccount: (SOGoMailAccount *) theAccount
+- (NSException *) updateFiltersForAccount: (SOGoMailAccount *) theAccount
                     withUsername: (NSString *) theUsername
                      andPassword: (NSString *) thePassword
                  forceActivation: (BOOL) forceActivation
 {
-  NSString *filterScript, *v, *content;
+  NSString *filterScript, *v, *content, *message;
   NSMutableArray *req;
   NSMutableString *script, *header;
   NSDictionary *result, *values;
+  NSException *error;
   SOGoUserDefaults *ud;
   SOGoDomainDefaults *dd;
   NGSieveClient *client;
@@ -853,16 +855,22 @@ static NSString *sieveScriptName = @"sogo";
   BOOL b, activate, dateCapability;
   unsigned int now;
 
+  error = nil;
   dd = [user domainDefaults];
   if (!([dd sieveScriptsEnabled] || [dd vacationEnabled] || [dd forwardEnabled]))
-    return YES;
+    return error;
 
   req = [NSMutableArray arrayWithCapacity: 15];
   ud = [user userDefaults];
 
   client = [self clientForAccount: theAccount  withUsername: theUsername  andPassword: thePassword];
   if (!client)
-    return NO;
+    {
+      error = [NSException exceptionWithHTTPStatus: 500 /* Server Error */
+                                            reason: @"Error while connecting to Sieve server."];
+      return error;
+    }
+
 
   // Activate script Sieve when forced or when no external script is enabled
   activate = forceActivation || ![self hasActiveExternalSieveScripts: client];
@@ -909,9 +917,12 @@ static NSString *sieveScriptName = @"sogo";
     }
   else
     {
-      [self errorWithFormat: @"Sieve generation failure: %@", [self lastScriptError]];
+      message = [NSString stringWithFormat: @"Sieve generation failure: %@", [self lastScriptError]];
+      [self errorWithFormat: message];
       [client closeConnection];
-      return NO;
+      error = [NSException exceptionWithHTTPStatus: 500 /* Server Error */
+                                            reason: message];
+      return error;
     }
 
   //
@@ -1137,7 +1148,7 @@ static NSString *sieveScriptName = @"sogo";
   result = [client deleteScript: sieveScriptName];
 
   if (![[result valueForKey:@"result"] boolValue])
-    [self logWithFormat: @"WARNING: Could not delete Sieve script - continuing...: %@", result];
+    [self warnWithFormat: @"Could not delete Sieve script: %@", [[result objectForKey: @"RawResponse"] objectForKey: @"reason"]];
 
   /* We put and activate the script only if we actually have a script
      that does something... */
@@ -1147,9 +1158,12 @@ static NSString *sieveScriptName = @"sogo";
 
       if (![[result valueForKey:@"result"] boolValue])
         {
-          [self logWithFormat: @"Could not upload Sieve script: %@", result];
+          message = [NSString stringWithFormat: @"Could not upload Sieve script: %@", [[result objectForKey: @"RawResponse"] objectForKey: @"reason"]];
+          [self errorWithFormat: message];
           [client closeConnection];
-          return NO;
+          error = [NSException exceptionWithHTTPStatus: 500 /* Server Error */
+                                            reason: message];
+          return error;
         }
 
       if (activate)
@@ -1157,15 +1171,18 @@ static NSString *sieveScriptName = @"sogo";
           result = [client setActiveScript: sieveScriptName];
           if (![[result valueForKey:@"result"] boolValue])
             {
-              [self logWithFormat: @"Could not enable Sieve script: %@", result];
+              message = [NSString stringWithFormat: @"Could not enable Sieve script: %@", [[result objectForKey: @"RawResponse"] objectForKey: @"reason"]];
+              [self errorWithFormat: message];
               [client closeConnection];
-              return NO;
+              error = [NSException exceptionWithHTTPStatus: 500 /* Server Error */
+                                                    reason: message];
+              return error;
             }
         }
     }
 
   [client closeConnection];
-  return YES;
+  return error;
 }
 
 @end
diff --git a/UI/PreferencesUI/UIxPreferences.m b/UI/PreferencesUI/UIxPreferences.m
index 95f4003bd..674b5d4b7 100644
--- a/UI/PreferencesUI/UIxPreferences.m
+++ b/UI/PreferencesUI/UIxPreferences.m
@@ -1613,6 +1613,7 @@ static NSArray *reminderValues = nil;
 
       if ([[user userDefaults] synchronize])
         {
+          NSException *error;
           SOGoMailAccount *account;
           SOGoMailAccounts *folder;
           SOGoDomainDefaults *dd;
@@ -1628,10 +1629,10 @@ static NSArray *reminderValues = nil;
                                                                                       inContext: context];
               account = [folder lookupName: @"0" inContext: context acquire: NO];
 
-              if (![account updateFiltersAndForceActivation: forceActivation])
+              if ((error = [account updateFiltersAndForceActivation: forceActivation]))
                 {
-                  results = (id <WOActionResults>) [self responseWithStatus: 502
-                           andJSONRepresentation: [NSDictionary dictionaryWithObjectsAndKeys: @"Connection error", @"message", nil]];
+                  results = (id <WOActionResults>) [self responseWithStatus: 500
+                                                      andJSONRepresentation: [NSDictionary dictionaryWithObjectsAndKeys: [error reason], @"message", nil]];
                 }
             }
           else