I have exchange 2013 with two send connectors as mentions below

1: Primary - Source Server MB1, MX2 , Destinations - Primary SMTP GW - Cost 1

2: Secondary  - Source Server MB1, MX2 , Destinations - Secondary SMTP GW - Cost 10

if the Primary SMTP GW  down, automatically it will not failover to Secondary Send connectors to send email througuth Secoundat SMT GW

 . sure if we disable firth connector, it will forward emails through seconds. but why it's not happing automatically whenever primary connector can't send email thought first connector ( we tested keep down one day for first SMTP GW , but didn't automatically failover send connector and send the emails. only after disable first connector and resubmit, then it sent the emails through seconds connectors.  

is it not automatically happned, if so, can anyone send office Microsoft site which says this is not automatic process and should be done by manualy process.

Thank you

indunil