Add FETCHMAIL_IMAP_DELETED_REMAINS_UNSEEN env' var.

Requested by Jonathan Buschmann, to suppress read-notifications on
servers such as MS Exchange or HP OpenMail.

3 files changed, 34 insertions, 6 deletions

diff --git a/NEWS b/NEWS
index b226dfd5..107c5f82 100644
--- a/NEWS
+++ b/NEWS
@@ -64,6 +64,9 @@ fetchmail-6.3.20 (not yet released):
 * fetchmail now always uses its own MD5 implementation.  The library and header
   variants are too diverse, and we've been bitten before -- and configure
   complains noisily on Cyrus-SASL's RFC1321 md5.h.
+* fetchmail now supports an environment variable to suppress marking deleted
+  messages as seen at the same time, FETCHMAIL_IMAP_DELETED_REMAINS_UNSEEN.
+  See the manual page for details. Requested by Jonathan Buschmann.
 
 # BUG FIXES
 * Call strlen() only once when removing CRLF from a line. (Sunil Shetye)
diff --git a/fetchmail.man b/fetchmail.man
index 903c8d4b..9e136f67 100644
--- a/fetchmail.man
+++ b/fetchmail.man
@@ -2781,6 +2781,14 @@ then that name is used as the default local name.  Otherwise
 session ID (this elaborate logic is designed to handle the case of
 multiple names per userid gracefully).
 
+.IP \fBFETCHMAIL_IMAP_DELETED_REMAINS_UNSEEN\fP
+(since v6.3.20):
+If this environment variable is set and not empty, fetchmail will NOT mark 
+messages retrieved through IMAP as \\Seen as they are deleted. On some servers, 
+for instance HP OpenMail and MS Exchange, this suppresses delivery 
+notifications. The default (if this variable is unset or empty) is to mark 
+messages as \\Seen and \\Deleted at the same time.
+
 .IP \fBFETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS\fP
 (since v6.3.17):
 If this environment variable is set and not empty, fetchmail will always load
diff --git a/imap.c b/imap.c
index 1364027f..86d1bfea 100644
--- a/imap.c
+++ b/imap.c
@@ -1311,6 +1311,22 @@ static int imap_delete(int sock, struct query *ctl, int number)
 /* set delete flag for given message */
 {
     int	ok;
+    /* Select which flags to set on message deletion: */
+    const char delflags_seen[] = "\\Seen \\Deleted";
+    const char delflags_unseen[] = "\\Deleted";
+    static const char *delflags;
+    /* Which environment variable to look for: */
+    const char dis_env[] = "FETCHMAIL_IMAP_DELETED_REMAINS_UNSEEN";
+
+    if (!delflags) {
+	char *tmp;
+	if ((tmp = getenv(dis_env)) != NULL && *tmp) {
+	    delflags = delflags_unseen;
+	} else {
+	    /* DEFAULT since many fetchmail versions <= 6.3.X */
+	    delflags = delflags_seen;
+	}
+    }
 
     (void)ctl;
     /* expunges change the fetch numbers */
@@ -1320,17 +1336,18 @@ static int imap_delete(int sock, struct query *ctl, int number)
      * Use SILENT if possible as a minor throughput optimization.
      * Note: this has been dropped from IMAP4rev1.
      *
-     * We set Seen because there are some IMAP servers (notably HP
-     * OpenMail) that do message-receipt DSNs, but only when the seen
-     * bit is set.  This is the appropriate time -- we get here right
+     * We set \Seen because there are some IMAP servers (notably HP
+     * OpenMail and MS Exchange) do message-receipt DSNs,
+     * but only when the seen bit gets set.
+     * This is the appropriate time -- we get here right
      * after the local SMTP response that says delivery was
      * successful.
      */
     if ((ok = gen_transact(sock,
 			imap_version == IMAP4 
-				? "STORE %d +FLAGS.SILENT (\\Seen \\Deleted)"
-				: "STORE %d +FLAGS (\\Seen \\Deleted)", 
-			number)))
+				? "STORE %d +FLAGS.SILENT (%s)"
+				: "STORE %d +FLAGS (%s)",
+			number, delflags)))
 	return(ok);
     else
 	deletions++;