Using phpmailer I keep getting a 110 timeout and "Unable to connect to host" when sending email from my web server.

The authentication details are right and they work on another server I have (login, pwd, ports etc and gmail acct set up for SSL connections on 465), but it's failing on my new server.

FIREWALL: I allow related/established, port 80 and a port for SSH on INPUT, then this on OUTPUT:

7906  474K DROP       tcp  --  any    any     anywhere             anywhere            tcp dpt:smtp  
0     0 ACCEPT     tcp  --  any    any     localhost.localdomain  yw-in-f109.1e100.net tcp dpt:submission  
0     0 ACCEPT     tcp  --  any    any     localhost.localdomain  gx-in-f109.1e100.net tcp dpt:ssmtp  
0     0 DROP       tcp  --  any    any     anywhere             anywhere            tcp dpt:submission  
9   540 DROP       tcp  --  any    any     anywhere             anywhere            tcp dpt:ssmtp 

This output chain works on my other server and disabling it doesn't get mail delivered either.

WEB SERVER: Varnish (80) > Nginx (8088) > Drupal 7 > PHP5-FPM > APC > MySQL All works beautifully, except for outgoing email.

What else could it be?
I understand phpmailer does NOT require a local MTA or procmail (this is sort of the point - I don't want the security or admin overhead of a full blown MTA on my web server). Am I wrong? Do I need an MTA as well?

What local ports and programs are used to authenticate over SSL and route mail using phpmailer?

Any ideas at all greatly appreciated - wasted a day on this nonsense already!