change tag to something unlikely, be less pessimistic about errors

imap/imap.go

@@ -12,7 +12,7 @@ import (
 )
 
 const (
-	tag      = ". "
+	tag      = "<<unreadMail>> "
 	other    = "* "
 	maxRead  = 11000000
 	timeout  = 3000 // ms
@@ -115,12 +115,13 @@ func searchUnseen(c *connection) stateFunc {
 }
 
 func fetch(c *connection, ids []int) stateFunc {
+	nErrs := 0
 	for _, id := range ids {
 		c.write(cmd(fmt.Sprintf("uid fetch %d body[]", id)))
-		if c.err == nil {
+		if len(c.err) == nErrs {
 			s := c.read("uid fetch of " + strconv.Itoa(id))
 			s = strings.TrimRight(s, ")\r\n")
-			if c.err == nil {
+			if len(c.err) == nErrs {
 				mail, err := parseMail(s)
 				if err == nil {
 					c.unreadMails = append(c.unreadMails, mail)
@@ -129,6 +130,7 @@ func fetch(c *connection, ids []int) stateFunc {
 				}
 			}
 		}
+		nErrs = len(c.err)
 	}
 	return logout
 }