diff --git a/src/utils/idfile.cpp b/src/utils/idfile.cpp
index 46626798..050e2204 100644
--- a/src/utils/idfile.cpp
+++ b/src/utils/idfile.cpp
@@ -57,20 +57,14 @@ static const int nmh = sizeof(mailhs) / sizeof(char *);
 
 const int wantnhead = 3;
 
-string idFile(const char *fn)
+// fn is for message printing
+static string idFileInternal(istream& input, const char *fn)
 {
     static int treat_mbox_as_rfc822;
     if (treat_mbox_as_rfc822 == 0) {
 	treat_mbox_as_rfc822 = getenv("RECOLL_TREAT_MBOX_AS_RFC822") ? 1 : -1;
     }
 
-    ifstream input;
-    input.open(fn, ios::in);
-    if (!input.is_open()) {
-	LOGERR(("idFile: could not open [%s]\n", fn));
-	return string();
-    }	    
-
     bool line1HasFrom = false;
     bool gotnonempty = false;
     int lookslikemail = 0;
@@ -162,6 +156,22 @@ string idFile(const char *fn)
     return string();
 }
 
+string idFile(const char *fn)
+{
+    ifstream input;
+    input.open(fn, ios::in);
+    if (!input.is_open()) {
+	LOGERR(("idFile: could not open [%s]\n", fn));
+	return string();
+    }
+    return idFileInternal(input, fn);
+}
+
+string idFileMem(const string& data)
+{
+    stringstream s(data, stringstream::in);
+    return idFileInternal(s, "");
+}
 
 #else
 
diff --git a/src/utils/idfile.h b/src/utils/idfile.h
index 6d75ffb8..bc484adf 100644
--- a/src/utils/idfile.h
+++ b/src/utils/idfile.h
@@ -21,10 +21,13 @@
 #include <string>
 #include <list>
 
-// Return mime type for file or empty string. The system's file utility does
-// a bad job on mail folders. idFile only looks for mail file types for now, 
-// but this may change
+// Look at data inside file or string, and return mime type or empty string. 
+//
+// The system's file utility does a bad job on mail folders. idFile
+// only looks for mail file types for now, but this may change
+
 extern std::string idFile(const char *fn);
+extern std::string idFileMem(const std::string& data);
 
 // Return all types known to us
 extern std::list<std::string> idFileAllTypes();