diff --git a/Source/ComposeBackEnd+GPGMail.m b/Source/ComposeBackEnd+GPGMail.m
index 3da68942..06ae81c8 100644
--- a/Source/ComposeBackEnd+GPGMail.m
+++ b/Source/ComposeBackEnd+GPGMail.m
@@ -1025,7 +1025,8 @@ - (void)MAUpdateSMIMEStatus:(CDUnknownBlockType)onComplete {
             // If there are already preferredSecurityProperties determined, copy the userShouldSignMessage and
             // userShouldEncryptMessage on to the new security properties.
             GMComposeMessagePreferredSecurityProperties *currentSecurityProperties = self.preferredSecurityProperties;
-            GMComposeMessagePreferredSecurityProperties *preferredSecurityProperties = [[GMComposeMessagePreferredSecurityProperties alloc] initWithSender:sender recipients:recipients userShouldSignMessage:currentSecurityProperties ? currentSecurityProperties.userShouldSignMessage : ThreeStateBooleanUndetermined userShouldEncryptMessage:currentSecurityProperties ? currentSecurityProperties.userShouldEncryptMessage : ThreeStateBooleanUndetermined];
+            GPGKey *signingKey = [currentSecurityProperties.signingSender isEqualToString:sender] ? currentSecurityProperties.signingKey : nil;
+            GMComposeMessagePreferredSecurityProperties *preferredSecurityProperties = [[GMComposeMessagePreferredSecurityProperties alloc] initWithSender:sender signingKey:signingKey recipients:recipients userShouldSignMessage:currentSecurityProperties ? currentSecurityProperties.userShouldSignMessage : ThreeStateBooleanUndetermined userShouldEncryptMessage:currentSecurityProperties ? currentSecurityProperties.userShouldEncryptMessage : ThreeStateBooleanUndetermined];
             preferredSecurityProperties.cachedSigningIdentities = [self valueForKey:@"_signingIdentities"];
             preferredSecurityProperties.cachedEncryptionCertificates = [self valueForKey:@"_encryptionCertificates"];
             
diff --git a/Source/GMComposeMessagePreferredSecurityProperties.h b/Source/GMComposeMessagePreferredSecurityProperties.h
index f846c089..6aaeb645 100644
--- a/Source/GMComposeMessagePreferredSecurityProperties.h
+++ b/Source/GMComposeMessagePreferredSecurityProperties.h
@@ -34,17 +34,22 @@ typedef enum {
     
     ThreeStateBoolean _userShouldSignMessage;
     ThreeStateBoolean _userShouldEncryptMessage;
+
+    GPGKey *_signingKey;
+    NSString *_signingSender;
 }
 
 + (GPGMAIL_SECURITY_METHOD)defaultSecurityMethod;
 
 - (id)initWithSender:(NSString *)sender recipients:(NSArray *)recipients;
-- (id)initWithSender:(NSString *)sender recipients:(NSArray *)recipients userShouldSignMessage:(ThreeStateBoolean)userShouldSignMessage userShouldEncryptMessage:(ThreeStateBoolean)userShouldEncryptMessage;
+- (id)initWithSender:(NSString *)sender signingKey:(GPGKey *)signingKey recipients:(NSArray *)recipients userShouldSignMessage:(ThreeStateBoolean)userShouldSignMessage userShouldEncryptMessage:(ThreeStateBoolean)userShouldEncryptMessage;
 
 - (void)addHintsFromBackEnd:(ComposeBackEnd *)backEnd;
 
 - (void)computePreferredSecurityPropertiesForSecurityMethod:(GPGMAIL_SECURITY_METHOD)securityMethod;
 
+- (void)updateSigningKey:(GPGKey *)signingKey forSender:(NSString *)sender;
+
 - (GPGKey *)encryptionKeyForDraft;
 
 @property (nonatomic, readonly, assign) BOOL canPGPSign;
@@ -81,6 +86,9 @@ typedef enum {
 @property (nonatomic, copy) NSString *sender;
 @property (nonatomic, copy) NSArray *recipients;
 
+@property (nonatomic, readonly, retain) GPGKey *signingKey;
+@property (nonatomic, readonly, retain) NSString *signingSender;
+
 @property (nonatomic, copy) NSDictionary *cachedSigningIdentities;
 @property (nonatomic, copy) NSDictionary *cachedEncryptionCertificates;
 
diff --git a/Source/GMComposeMessagePreferredSecurityProperties.m b/Source/GMComposeMessagePreferredSecurityProperties.m
index 3c578cde..f2af1b8f 100644
--- a/Source/GMComposeMessagePreferredSecurityProperties.m
+++ b/Source/GMComposeMessagePreferredSecurityProperties.m
@@ -57,10 +57,12 @@ - (id)initWithSender:(NSString *)sender recipients:(NSArray *)recipients {
     return self;
 }
 
-- (id)initWithSender:(NSString *)sender recipients:(NSArray *)recipients userShouldSignMessage:(ThreeStateBoolean)userShouldSign userShouldEncryptMessage:(ThreeStateBoolean)userShouldEncrypt {
+- (id)initWithSender:(NSString *)sender signingKey:(GPGKey *)signingKey recipients:(NSArray *)recipients userShouldSignMessage:(ThreeStateBoolean)userShouldSign userShouldEncryptMessage:(ThreeStateBoolean)userShouldEncrypt {
     if((self = [self initWithSender:sender recipients:recipients])) {
         _userShouldSignMessage = userShouldSign;
         _userShouldEncryptMessage = userShouldEncrypt;
+        _signingKey = [signingKey copy];
+        _signingSender = [sender copy];
     }
     
     return self;
@@ -125,6 +127,13 @@ - (GPGKey *)encryptionKeyForDraft {
     return [[GPGMailBundle sharedInstance] anyPersonalPublicKeyWithPreferenceAddress:senderAddress];
 }
 
+- (void)updateSigningKey:(GPGKey *)signingKey forSender:(NSString *)sender {
+    // Once a signing key is set, the keyring is no longer queried for a key matching
+    // the signer address, but the set signing key is always used. (#895)
+    _signingKey = [signingKey copy];
+    _signingSender = [sender copy];
+}
+
 - (void)computePreferredSecurityPropertiesForSecurityMethod:(GPGMAIL_SECURITY_METHOD)securityMethod {
     // Load signing identity and certificates for S/MIME.
     NSMutableDictionary *signingIdentities = [self.cachedSigningIdentities mutableCopy];
@@ -187,14 +196,23 @@ - (void)computePreferredSecurityPropertiesForSecurityMethod:(GPGMAIL_SECURITY_ME
             signingKey = nil;
         }
         if(!signingKey) {
-            NSArray *signingKeyList = [[[GPGMailBundle sharedInstance] signingKeyListForAddress:senderAddress] allObjects];
-            // TODO: Consider pereferring the default key if one is configured.
-            signingKeys[senderAddress] = [signingKeyList count] > 0 ? signingKeyList[0] : [NSNull null];
-            // In order to trick mail into accepting the key, it has to be added under the sender
-            // with email and full name as well. Otherwise, the last check before calling
-            // -[ComposeBackEnd _makeMessageWithContents:isDraft:shouldSign:shouldEncrypt:shouldSkipSignature:shouldBePlainText:]
-            // will disable signing, since no key for the full address can be found in the _signingIdentities dictionary.
-            signingKeys[sender] = signingKeys[senderAddress];
+            // If a particular signing key has been chosen from the "From" field,
+            // always use that key. Otherwise query all signing keys matching the address.
+            // (#895)
+            if(_signingKey && [_signingSender isEqualToString:sender]) {
+                signingKeys[senderAddress] = _signingKey;
+                signingKeys[sender] = signingKeys[senderAddress];
+            }
+            else {
+                NSArray *signingKeyList = [[[GPGMailBundle sharedInstance] signingKeyListForAddress:senderAddress] allObjects];
+                // TODO: Consider pereferring the default key if one is configured.
+                signingKeys[senderAddress] = [signingKeyList count] > 0 ? signingKeyList[0] : [NSNull null];
+                // In order to trick mail into accepting the key, it has to be added under the sender
+                // with email and full name as well. Otherwise, the last check before calling
+                // -[ComposeBackEnd _makeMessageWithContents:isDraft:shouldSign:shouldEncrypt:shouldSkipSignature:shouldBePlainText:]
+                // will disable signing, since no key for the full address can be found in the _signingIdentities dictionary.
+                signingKeys[sender] = signingKeys[senderAddress];
+            }
         }
         canPGPSign = signingKeys[senderAddress] && signingKeys[senderAddress] != [NSNull null] ? YES : NO;
     }
diff --git a/Source/HeadersEditor+GPGMail.m b/Source/HeadersEditor+GPGMail.m
index ae9adbb0..db2f44a9 100644
--- a/Source/HeadersEditor+GPGMail.m
+++ b/Source/HeadersEditor+GPGMail.m
@@ -704,9 +704,16 @@ - (void)MAChangeFromHeader:(NSPopUpButton *)sender {
     else
         [button addItemWithTitle:(parentItem ? parentItem : item).title];
     
-    // Set the selected key in the back-end.
-	ComposeBackEnd *backEnd = [GPGMailBundle backEndFromObject:self];
-	[backEnd setIvar:@"gpgKeyForSigning" value:[item getIvar:kHeadersEditorFromControlGPGKeyKey]];
+    ComposeBackEnd *backEnd = [GPGMailBundle backEndFromObject:self];
+    GMComposeMessagePreferredSecurityProperties *securityProperties = [(ComposeBackEnd_GPGMail *)backEnd preferredSecurityProperties];
+    GPGKey *signingKey = [item getIvar:kHeadersEditorFromControlGPGKeyKey];
+    if(signingKey) {
+        // Configure the security properties to always used the specified key for signing,
+        // instead of looking up a matching key using the signers email address.
+        // This is especially necessary in case multiple signing keys are available for the
+        // same email address. (#895)
+        [securityProperties updateSigningKey:signingKey forSender:item.representedObject];
+    }
     
     [self MAChangeFromHeader:button];
 }