Updated FAQ

FAQ.md

@@ -997,6 +997,7 @@ There are general errors and errors specific to Gmail accounts (see below).
 
 **General errors**
 
+<a name="authfailed"></a>
 The error *... Authentication failed ...* or *... AUTHENTICATE failed ...* likely means that your username or password was incorrect.
 Some providers expect as username just *username* and others your full email address *username@example.com*.
 When copying/pasting to enter a username or password, invisible characters might be copied, which could cause this problem as well.
@@ -1040,6 +1041,12 @@ see [here](https://blogs.technet.microsoft.com/pki/2010/09/30/sha2-and-windows/)
 
 The errors *... Read error ...*, *... Write error ...*, *... Read timed out ...*, *... Broken pipe ...* mean that the email server is not responding anymore or that the internet connection is bad.
 
+<a name="connectiondropped"></a>
+The error *... Connection dropped by server? ...* means that the email server unexpectedly terminated the connection.
+This sometimes happen when there were too many connections in a too short time or when a wrong password was used for too many times.
+In this case, please make sure your password is correct and disable receiving in the receive settings for about 30 minutes and try again.
+If needed, see [this FAQ](#user-content-faq23) about how you can reduce the number of connections.
+
 The error *... Unexpected end of zlib input stream ...* means that not all data was received, possibly due to a bad or interrupted connection.
 
 The error *... connection failure ...* could indicate [Too many simultaneous connections](#user-content-faq23).