UPDATE - The Vodafone 360 service will be terminated on December 31st, 2011. After this time Vodafone will not provide an SMTP service to customers. It is advised, if the below description applies to you, to switch to a free Google or Hotmail email account and use the SMTP settings for that service. Alternately there are paid SMTP relay services available, such as www.smtpauth.com
When you set up a POP or IMAP-based email account on your phone, to send email you need to also specify an outgoing SMTP mail server. Due to security concerns, most ISPs require that you use their Internet service in order to be able to use their outgoing mail server. Therefore, if setting up a Tiscali email account for example, whereas your incoming mail server would be Tiscali's, your outgoing mail server may vary depending on how you're connecting to the Internet. In the case of Vodafone UK, the outgoing mail server to use would have been "send.vodafone.net" - an SMTP server provided by Vodafone to allow their subscribers to send email messages when connected to the Vodafone data network.
This server now appears to have been retired, but it is still possible to send email via SMTP on the Vodafone UK network.
You will first need to sign up for a free Vodafone 360 account. This only takes a few moments and can be done online by browsing to www.vodafone360.com
The setting to use on your phone are then as follows:
SMTP (Outgoing) server - smtp.360.com
Username - firstname.lastname@example.org - where "username" is what you selected when you signed up for the 360 account
Password - your 360 password
Security - SSL / TLS
Port - 465
You should now be able to send email via SMTP.
This does not apply to BlackBerry or Exchange ActiveSync accounts which operate differently.