Outgoing emails OK by WiFi at home but no go elsewhere

If I'm away from home I can't send outgoing emails. I can receive emails, access internet etc OK but cannot send an email (gets stuck in Outbox). When I'm at home using WiFi I don't have this problem.

I contacted my phone service provider (Vodafone) and my ISP (Internode) , both discussions focussed on my email account settings but in the end they agreed my settings were correct, suggesting this is perhaps an SGS issue.

I am in Adelaide, Australia and my firmware is Froyo (2.2).
Outgoing Account Settings:
 - SMTP server: securemail.internode.on.net
 - Port: 465
 - Security Type: SSL (All certificates accepted)
 - Require sign in - ticked

Any suggestions appreciated.

That's not the issue since my ISP helpdesk was surprised when it wouldn't work, even after we tried a few different email account security settings. They said people with other don't experience this problem and it must be SGS unique.