Well, I'm not getting anywhere with this. I've been having a discussion with their customer care dept and since they're so hopeless I've decided to post a transcript of the email thread here. It started with me explaining the problem below, and asking how I can set my phone up so that
a) It'll use my smtp server, rather than theirs

It'll work over their GPRS network, reliably
c) It'll work over my wi-fi/adsl connection at home.
Here's how it's going so far:
Vodafone customer services said:
Sent: 23 April 2008 13:02
Subject: Re: SubmitContactUsQuery
Hi Mr. Otway,
Thanks for your email to Vodafone about the problem for accessing your email from your mobile phone. Let me see what needs to be done.
I am sorry to learn that you are unable to access your emails from your mobile phone. I apologise to you for the inconvenience caused to you.
Mr. Otway, I would like to let you know that we have a separate dedicated team to solve all the technical queries of our customers. You need to contact our technical team on 191 from your mobile phone or 0870 700 191 from a landline and select option 2 and 2. I am sure that one of my colleagues will be pleased to assist you with all of your query.
I am sorry I was unable to help you. If there is anything else I can help you with, please feel free to contact me.
Kind regards,
Vodafone Customer Services
Webreaper said:
Hi,
Why is it that every time I email your customer support, I wait 2 days and get a complete waste-of-time response? It's just a waste of my time, frankly.
I am not having problems accessing my email. My email is fine. I am having problems with vodafone intercepting my access to my email, and with vodafone's email servers being completely unreliable.
I have put ALL the information required for a technician to answer my question in my original email. Please give the email to somebody who has a clue technically, and ask them to read it and answer it.
I'd also appreciate if you could flag my account to a customer services manager and ask them to review my correspondence history via email. I think you'll agree it is FAR from satisfactory.
Thank you
Vodafone customer services said:
Hi
I'm sorry to hear you've been having problems you're having with your SMTP server.
The error message you're receiving "the server was unable to send email at this time" isn't a message which is sent by Vodafone and this would have come from your mail provider.
Vodafone don't hijack port 25 traffic and route this to our own SMTP servers as this port is an open port.
You would need to change the settings and change the SMTP settings to send.vodafone.net as explained in the previous email and as advised by our Technical Team.
I've made my manager aware of your situation and if you feel this needs escalating further, please give us a call and let us know.
I hope I've explained everything Mark.
Kind regards,
Vodafone Customer Services
Webreaper said:
Sent: 28 April 2008 12:05
To:
[email protected]
Subject: RE: SubmitContactUsQuery
Hi there,
Some of the response in this email just doesn't make sense.
Firstly, I run my own Smtp server on co-located in telehouse. It absolutely will not return the message below - this must be a vodafone message.
Secondly, my smtp server works flawlessly when not using voda gprs (and has done for the last 8 or so years). So how do you explain that randomly I see this error whilst using gprs, but if I switch to send.vodafone.net it always works? There is clearly some traffic manipulation going on. My smtp server always works flawlessly over wifi (ie not using voda's network).
Lastly, I do not understand your 4th para. If you do not interfere with my smtp traffic, why would I need to switch to send.vodafone.net? And, more importantly, why would I - as it doesn't work over wifi (on a non vodafone network). I do not want to have to switch my smtp settings every time I switch from gprs to wifi.
This all worked without any problems up until a few weeks ago (I have never used the send.vodafone.net server before March 08). Please tell me what I can do to make my phone connect to my smtp server reliably over your gprs network.
Regards
Vodafone customer services said:
Hi,
I've spoken to our technical team again and they've advised the SMTP server must be set as send.vodafone.net (if this fails, please try smtp.vodafone.net). This can't be set as anything else as this won't work.
You may find some more useful tips at www.vodafone.co.uk by clicking on help centre.
I've also attached a short customer feedback questionnaire and would really appreciate your thoughts to help us improve our service and I can assure you, this will be treated in confidence. Just click here to start.
Best Wishes,
Vodafone Customer Services
Webreaper said:
Sent: 29 April 2008 13:33
To:
[email protected]
Subject: RE: SubmitContactUsQuery
Hi there,
For about the 5th time, can you please try reading the email thread before replying.
Why won't "anything else work"? I was told in an earlier email that Voda do not capture port 25 traffic and that I can use my own smtp server. If I use smtp.vodafone.net, it means I cannot send when my phone is connected using wi-fi, as your smtp auth on that server is done by the current connection details.
I am pleading with you now, please can you stop switching what you say (alternating between "yes, you can use your own smtp server" and "no, you need to use send.vodafone.net") and tell me how I can fix this problem. If you do not give me a satisfactory answer then I may cancel my contract as you clearly can't povide the service you promised (mobile email on the move).
Please find somebody technical who understands smtp protocols and ask them to re-read the entire thread and respond.
As for your survey, I'd love to respond, but I fear your (usually faulty) adult content filtering system would explode with the expletives I'd be tempted to use.
Regards
Why are Vodafone so completely incapable of just getting a technician to answer my question? And do they seriously expect all Voda smartphone/PDA users to use the vodafone Smtp server, and then not be able to send any emails when connected over a non-Vodafone wireless network, or using Activesync??
Absolute total and complete muppets, the lot of them.