smtp unable to connect in Zimbra email client

I am able to connect to the incoming iCloud server and am receiving my emails. However I can not connect to the SMTP outgoing server.

smtp.mail.me.com using SSL encryption port 587 although the software defaults to 465 but I override and have tried connecting using both.

I supply my name, email and password (setup app specific password that is working for incoming server not for outgoing server)

this is the message i get service.FAILURE: system failure: SMTP connect failure.

Appreciate any help!

Norm