Nope tried that. The emails still come back on the next send and recieve.

That works but how do you then empty inbox.trash? The emails placed there never seem to get deleted!

Has *anyone* managed to delete mail from their IMAP account (from their server) using their phone's mail client?

The problem is that the Windows Mobile Messaging application doesn't use the normal IMAP deletion system.  Usually an IMAP client will simply set a flag on the server to indicate the message is marked for deletion.  For example, Outlook users periodically hit "ALT+E,S" to purge the messages marked for deletion from the server.  Outlook Express has an option to purge when leaving an IMAP folder. 

Windows Mobile instead moves the local copy (not the IMAP server copy) to the deleted items folder.  When you "purge", you're actually just deleting it from the server.

Interestingly, Entourage (the MS Office Outlook equivalent on the Mac) does this similar to WM, except that it actually moves the message to the deleted items folder on the server.  I've heard Outlook's development has been taken over by the Office for Mac team, so perhaps we'll see this "innovation" moved to Outlook as well (I use quotes because you can't move messages between folders in IMAP.  When you "move" a message, you're actually downloading the entire message, then uploading it back to the server in the new folder.  On slow connections this takes forever).

Anyway, you can control the WM Messaging behavior somewhat.  On the PocketPC:

Tap Accounts from the Messaging menu bar.
Tap "Accounts..." in the pop-up menu.
Select the "Storage" tab.
Adjust the "Empty deleted items:" field to the value you want.

The 3 values are

Immediately - purges the deleted item when you mark it as deleted while connected or upon connection.
On connect/disconnect - purges upon connection.  If you delete something while you're still downloading messages this does NOT delete it immediately.  There has to be another connection (purge is done at the beginning of the connection routine, I guess?).  Until this is done, nothing happens on the server.
Manually - You choose when to purge using Tools -> Empty Deleted Items.

On my Smartphone this seems to be locked to the "On connect/disconnect" option based on my brief testing.  If you get in the habit of performing a "Send/Receive" after deleting messages, you'll be fine.  I don't see any UI in the Smartphone messaging application to change this.  I looked briefly in the PocketPC registry and couldn't figure out where this option is saved.  I suspect if someone located this option on the PocketPC it could be changed on the Smartphone as well.

The problem is that the Windows Mobile Messaging application doesn't use the normal IMAP deletion system.  Usually an IMAP client will simply set a flag on the server to indicate the message is marked for deletion.  For example, Outlook users periodically hit "ALT+E,S" to purge the messages marked for deletion from the server.  Outlook Express has an option to purge when leaving an IMAP folder. 

Windows Mobile instead moves the local copy (not the IMAP server copy) to the deleted items folder.  When you "purge", you're actually just deleting it from the server.

Interestingly, Entourage (the MS Office Outlook equivalent on the Mac) does this similar to WM, except that it actually moves the message to the deleted items folder on the server.  I've heard Outlook's development has been taken over by the Office for Mac team, so perhaps we'll see this "innovation" moved to Outlook as well (I use quotes because you can't move messages between folders in IMAP.  When you "move" a message, you're actually downloading the entire message, then uploading it back to the server in the new folder.  On slow connections this takes forever).

Anyway, you can control the WM Messaging behavior somewhat.  On the PocketPC:

Tap Accounts from the Messaging menu bar.
Tap "Accounts..." in the pop-up menu.
Select the "Storage" tab.
Adjust the "Empty deleted items:" field to the value you want.

The 3 values are

Immediately - purges the deleted item when you mark it as deleted while connected or upon connection.
On connect/disconnect - purges upon connection.  If you delete something while you're still downloading messages this does NOT delete it immediately.  There has to be another connection (purge is done at the beginning of the connection routine, I guess?).  Until this is done, nothing happens on the server.
Manually - You choose when to purge using Tools -> Empty Deleted Items.

On my Smartphone this seems to be locked to the "On connect/disconnect" option based on my brief testing.  If you get in the habit of performing a "Send/Receive" after deleting messages, you'll be fine.  I don't see any UI in the Smartphone messaging application to change this.  I looked briefly in the PocketPC registry and couldn't figure out where this option is saved.  I suspect if someone located this option on the PocketPC it could be changed on the Smartphone as well.

Thanks for your detailed reply.

Just one point however regarding the smartphone,  if you delete then do a send & receive immediately  the deleted emails do indeed go, but when you do another send & receive they just come bounding back.

I honestly feel IMAP on the smartphone is totally unusable.

I'm talking about the smartphone here not the Pocket PC.

I think the problem is with the smartphone software and not me.

Have you actually tried it on a smartphone?

I am using an SDA with 2003SE.

How are you deleting your emails - just by selecting menu/1?

And then they never come back if you do a couple of S/R?

I have just deleted and re-created my IMAP account and it makes no difference.

I also have a C500 and that does exactly the same thing. 

I'm not sure what you are doing and I am not.

I've never seen an email re-appear.  I've tried S/R a few times after deleting and it never shows up again.

Too bad deleting the account didn't help.  That was certainly the easiest solution. 

Do you have any information on the OS / IMAP server you're using?  Both of mine are Exchange servers.  Maybe MS is doing something strange on the server in my case.  Wouldn't be the first time they slipped something like that in. 

Hmm.  I'm not using an exchange server.  It's just a standard linux box that supports POP & IMAP.

IMAP works fine from Outlook 2003 though.

Whether Outlook works or not doesn't matter since the way message deletion is done with WM2003 is completely different (as I described earlier).  You wanted a likely reason, I'm guessing it has something to do with the way WM2003 and your IMAP server are interacting.  I suspect the other forum poster has a similar server.  You might want to compare the IMAP server, version number, and configuration with the other poster to see if there's something in common there.