diff --git a/uppsrc/Core/Inet.h b/uppsrc/Core/Inet.h
index f677e79fa..52a5336e9 100644
--- a/uppsrc/Core/Inet.h
+++ b/uppsrc/Core/Inet.h
@@ -12,7 +12,7 @@ String UrlDecode(const char *s, int len);
 String UrlDecode(const String& s);
 
 String QPEncode(const char* s);
-String QPDecode(const char *s);
+String QPDecode(const char *s, bool undescore_to_space = false);
 
 String Base64Encode(const char *s, const char *end);
 String Base64Encode(const char *s, int len);
diff --git a/uppsrc/Core/InetUtil.cpp b/uppsrc/Core/InetUtil.cpp
index bc1e61fda..f2fe6f1cc 100644
--- a/uppsrc/Core/InetUtil.cpp
+++ b/uppsrc/Core/InetUtil.cpp
@@ -175,7 +175,7 @@ String QPEncode(const char* s)
 	int len = 0;
 	const int  limit  = 70;
 	while(*s) {
-		if(s[0] >= 33 && s[0] <= 126 && s[0] != '=') {
+		if(s[0] >= 33 && s[0] <= 126 && s[0] != '=' && s[0] != '_') {
 			r.Cat(s[0]);
 			len++;
 		}
@@ -188,8 +188,8 @@ String QPEncode(const char* s)
 			len = 0;
 		}
 		else // Encode HT or SP only if they are at the end of line (before CRLF or EOF)
-		if((s[0] == ' ' || s[0] == '\t') 	&&
-		   (s[1] && s[1] != '\n') 		&&
+		if((s[0] == ' ' || s[0] == '\t') &&
+		   (s[1] && s[1] != '\n') &&
 		   (s[1] != '\r' || (s[1] == '\r' && s[2] && s[2] != '\n'))) {
 			r.Cat(s[0]);
 			len++;
@@ -212,7 +212,7 @@ String QPEncode(const char* s)
 	return r;
 }
     
-String QPDecode(const char *s)
+String QPDecode(const char *s, bool underscore_to_space)
 {
 	StringBuffer r;
 	while(*s) {
@@ -226,6 +226,9 @@ String QPDecode(const char *s)
 			if(IsXDigit(c1) && IsXDigit(c2))
 				r.Cat((ctoi(c1) << 4) | ctoi(c2));
 		}
+		else
+		if(underscore_to_space && c == '_')
+			r.Cat(' ');
 		else
 			r.Cat(c);
 	}
diff --git a/uppsrc/Core/POP3/InetMessage.cpp b/uppsrc/Core/POP3/InetMessage.cpp
index 7de747570..4241aee19 100644
--- a/uppsrc/Core/POP3/InetMessage.cpp
+++ b/uppsrc/Core/POP3/InetMessage.cpp
@@ -11,14 +11,12 @@ String QDecode(const String& s)
 		return s;
 	if(begin != "=" || end != "=")
 		return s;
-	if(ToUpper(enc) == "B")
+	enc = ToUpper(enc);
+	if(enc == "B")
 		r = Base64Decode(txt);	
 	else
-	if(ToUpper(enc) == "Q") {
-		txt.Replace(" ", "_");		
-		r = QPDecode(txt);
-		r.Replace("_", " ");
-	}
+	if(enc == "Q")
+		r = QPDecode(txt, true);
 	else
 		return s;
 	int charset = CharsetByName(chs);
@@ -88,7 +86,7 @@ String sEncode(const String& text)
 			String txt = ToCharset(CHARSET_UTF8, text);
 			String r = "=?UTF-8?Q?";
 			for(const char *s = txt; *s; s++) {
-				if((byte)*s < ' ' || (byte)*s > 127 || findarg(*s, '=', '?', ' ', ',') >= 0)
+				if((byte)*s < ' ' || (byte)*s > 127 || findarg(*s, '=', '?', ' ', ',', '_') >= 0)
 					r << '=' << FormatIntHexUpper((byte)*s, 2);
 				else
 					r.Cat(*s);
diff --git a/uppsrc/Core/src.tpp/Inet$en-us.tpp b/uppsrc/Core/src.tpp/Inet$en-us.tpp
index fdb6773dc..85aabd3c2 100644
--- a/uppsrc/Core/src.tpp/Inet$en-us.tpp
+++ b/uppsrc/Core/src.tpp/Inet$en-us.tpp
@@ -59,13 +59,15 @@ IME type application/x`-www`-form`-urlencoded] (see UrlEncode).&]
 [s5;:QPEncode`(const char`*`): [_^String^ String]_[* QPEncode]([@(0.0.255) const]_[@(0.0.255) c
 har`*]_[*@3 s])&]
 [s2;%% Encodes string to [^http`:`/`/en`.wikipedia`.org`/wiki`/Quoted`-printable^ quote
-d`-printable] format .&]
+d`-printable] format.&]
 [s3;%% &]
 [s4; &]
-[s5;:QPDecode`(const char`*`): [_^String^ String]_[* QPDecode]([@(0.0.255) const]_[@(0.0.255) c
-har]_`*[*@3 s])&]
+[s5;:QPDecode`(const char`*`,bool`): [_^String^ String]_[* QPDecode]([@(0.0.255) const]_[@(0.0.255) c
+har]_`*[*@3 s], [@(0.0.255) bool]_[*@3 underscore`_to`_space]_`=_[@(0.0.255) false])&]
 [s2;%% Decodes string from [^http`:`/`/en`.wikipedia`.org`/wiki`/Quoted`-printable^ quo
-ted`-printable] format .&]
+ted`-printable] format. If [%-*@3 s] [%-*@3 underscore`_to`_space] 
+is true, function replaces `'`_`' with space `' `' (as required 
+by [^http`:`/`/en`.wikipedia`.org`/wiki`/MIME`#Encoded`-Word^ encoded`-word]).&]
 [s3;%% &]
 [s4; &]
 [s5;:Base64Encode`(const char`*`,const char`*`): [_^String^ String]_[* Base64Encode]([@(0.0.255) c