iphone and plusnet mail

[#1]

Yes, I know, it's an extravagance but hey, you can't take it with you
I have an iPhone and have successfully sync'd it with my mac computer, and everything works fine via my wifi connection. Also everything works except mail via GPRS and EDGE. Now I know that my account SMTP is set for plusnet (relay.plus.net). Out of range of a plusnet connection I can receive mail but I'm unable to send mail via GPRS and EDGE (obviously).
now I've set up a new account with all the same info except the smtp bit which I believe is smtp.o2.co.uk but no joy with that. Is there a surefire way to send email using 'Mail' (rather than webmail) without the tears?
INFO:
I am only using one email address on my iPhone so it should be pretty straight forward but I think I'm missing a trick somewhere.
Any clues anyone?

[#2]

Use SMTP auth. As long as you have a subscription account with us then you should be able to use your username and password to send email regardless as to who you're connected with.

[#3]

Quote from: Bob

Use SMTP auth. ......

Sorry, being a bit dim this morning Bob. Do you mean replace relay.plus.net with SMTP auth ? on the only account on the iphone?

[#4]

No, set-up to use authentication on relay.plus.net. I don't know the iphone but there should be a way to select authentication on the SMTP connection then enter your portal login and password as the authentication details.

[#5]

This should help:
http://community.plus.net/forum/index.php/topic,60436.msg491483.html#msg491483

[#6]

Quote from: ruslyn

This should help: http://community.plus.net/forum/index.php/topic,60436.msg491483.html#msg491483

Good link, will try it when I have a minute.
Particularly good tip if you screw up settings on the iphone (Like I did last night) just plug in to sync computer and it sorts it all out for you again! 
[edit]
Just a thought. would this be the same if using my laptop on a bt openzone hotspot? coz I've been changing 'relay.plus.net' to 'smtp.btopenzone.com' every time.

[#7]

Yes.
Authenticated SMTP can be used on non-plusnet networks. In fact you can also use it on PNs network so once set, you don't need to change it moving to/from PN.

[#8]

blooooomin' marvelous, all these years 
You learn something new all the time 

[#9]

FYI: Authenticated SMTP was only implemented just before Christmas so it was not possible to use it before then. It has also not been widely publicised.

[#10]

Okay, many thanks for the help folks it all works correctly now. and as the link above suggests do it on the sync computer then sync the phone to it rather than the other way round. 
Cheers all, now off to watch the rugby!! C'mon England.