Mobile email sending problem

[#1]

I have an HTC Kaiser with a T mobile contract. I have set up 2 plusnet email a/cs on the phone but cannot send through them although can receive. Can anyone advise where my settings might be wrong? Incoming mail server = mail.plus.net, a/c type = POP3, outgoing SMTP mail server = relay.plus.net. Maybe a T mobile problem, but I have another non plusnet a/c set up which works fine -

[#2]

You can't use relay.plus.net from an non PN IP address without using authenticated SMTP.
T-mobile to have a relay you can use smtp.t-mobile.co.uk change your settings to that.

[#3]

I was under the impression that you could now use relay.plus.net as an authenticated server (without ticking any boxes that say Secure Password Authentication) to send email from any ISP connection. You need to use your main username and password (used to log into Plusnet website) and not the username and password for the mailbox in use to enable you to log in correctly to the server.

[#4]

Yes you can do that, as I did state in my original post, however your password is sent as clear text.
As T Mobile have a relay to use without any authentication it seems easier and more secure to use that.

[#5]

thanks adiewoo for your advice, which pointed me in the right direction. The t mobile outgoing server is actually  smtp.t-email.co.uk. When I used this I could finally send emails from my phone. So 8 out of 10, but I still wouldn't have got there without you! Btw seems impossible to find correct setting son t mobile's web site, had to do a google search and found all operators settings here: http://www.knowyourmobile.com./info/1310/uk_mobile_operators_internet_and_email_settings.html