emsmdb, zcore: perform dot-stuffing ahead of SMTP DATA

Certain lines in a mail have special meaning to certain components in
the chain, such as lines beginning with "From " in the Unix mbox
format, or lines beginning with a "." in a SMTP DATA command.

When regular mail is prepared for export, MIME::write_content always
applies a transform, and that is base64 or, (since recently)
alternatively, quoted-printable. The base64 transform naturally
"defuses" lines since neither "From " nor "." are possible with the
base64 output alphabet. The QP encoder specifically looks for the
special pattern and force-encodes them. By doing all that, no SMTP
dot-stuffing would be needed.

However, S/MIME is not classified as regular mail and would be copied
verbatim to the SMTP channel, which is incorrect.

Change the send routines to explicitly do SMTP-style dot-stuffing.

References: GXF-30, GXL-84

exch/emsmdb/common_util.cpp

@@ -1676,6 +1676,12 @@ BOOL common_util_send_mail(MAIL *pmail,
 	char last_command[1024];
 	char last_response[1024];
 
+	MAIL dot_encoded(pmail->pmime_pool);
+	if (pmail->check_dot()) {
+		if (!pmail->transfer_dot(&dot_encoded, true))
+			return false;
+		pmail = &dot_encoded;
+	}
 	int sockd = gx_inet_connect(g_smtp_ip, g_smtp_port, 0);
 	if (sockd < 0) {
 		log_err("Cannot connect to SMTP server [%s]:%hu: %s",

exch/zcore/common_util.cpp

@@ -1360,6 +1360,12 @@ static BOOL common_util_send_mail(MAIL *pmail,
 	char last_command[1024];
 	char last_response[1024];
 
+	MAIL dot_encoded(pmail->pmime_pool);
+	if (pmail->check_dot()) {
+		if (!pmail->transfer_dot(&dot_encoded, true))
+			return false;
+		pmail = &dot_encoded;
+	}
 	int sockd = gx_inet_connect(g_smtp_ip, g_smtp_port, 0);
 	if (sockd < 0) {
 		log_err("Cannot connect to SMTP server [%s]:%hu: %s",

lib/email/mail.cpp

@@ -827,12 +827,12 @@ bool MAIL::dup(MAIL *pmail_dst)
 }
 
 /*
- *	apply or reverse-apply dot-stuffing mail object into a clean object
+ *	add or remove dot-stuffing; copies into a clean object
  *	@param
  *		pmail_src [in]			mail source object
  *		pmail_dst [in, out]		mail destination object
  */
-bool MAIL::transfer_dot(MAIL *pmail_dst, bool fwd)
+bool MAIL::transfer_dot(MAIL *pmail_dst, bool add_dot)
 {
 	auto pmail_src = this;
 	unsigned int size;
@@ -866,7 +866,7 @@ bool MAIL::transfer_dot(MAIL *pmail_dst, bool fwd)
 		size ++;
 		pbuff[offset + size] = '\n';
 		size ++;
-		if (fwd) {
+		if (add_dot) {
 			if (pbuff[offset] == '.') {
 				memmove(&pbuff[offset+1], &pbuff[offset], size);
 				++size;