fix trailing spaces problem

Author: pedrobsaila

xml/System.Net.Mail/MailAddress.xml

@@ -70,7 +70,7 @@ Within these two formats, the following elements are allowed:
 
 -   A <xref:System.Net.Mail.MailAddress.User%2A> name with quotes. For example, `"user name"@host`.  
   
--   Consecutive and trailing dots in user names. For example, `user...name..@host`.  
+-   Trailing dot in user names. For example, `username.@host`.  
   
 -   Bracketed domain literals. For example, `<user@[my domain]>`.  
   
@@ -107,6 +107,8 @@ The <xref:System.Net.Mail.MailAddress> class does not support the following mail
 - Groups, as defined in RFC 2822 Section 3.4 published by the IETF.  
   
 - The obsolete user name formats of `"user"."name"@host`, `user."name"@host` or `"user".name@host`.
+
+- Consecutive dots as specified in RFC 2822 section 3.4.1. For example, `user...name@host` or ``[email protected]``.