Q:

Reply-to e-mail address using CiviMail in 4.6.3 defaults to system default

We recently upgraded to 4.6.3, and now the reply-to email address in CiviMail e-mails defaults to the system e-mail, not the From sender e-mail address, as previously.  I could not duplicate on the demo site (at http://d46.demo.civicrm.org ), perhaps because the demo site is running 4.6.5. 
A real bummer, any help fixing appreciated.  Was this a 4.6.3 bug that has now been fixed in 4.6.5?  
Thanks.  

A:

This does indeed appear to be a bug in 4.6.3.   Upgrading to 4.6.4 will fix the problem. 
Note that additional functionality in CiviMail can affect the from: address: Using VERP or the custom reply-to header.