Thanks for the suggestions everyone came up with. You're not going to 
believe what fixed it!

I did already have "fixup protocol ftp 21" on the PIX, although I don't 
run any ftp servers. It seems that this is a default on a new box. I tried 
disabling this, and now I can ftp to the hosting provider. However this 
prevents the use of outgoing active FTP connections from inside the PIX, 
and so breaks one of my critical applications that uses an FTP component 
that doesn't appear to allow PASV to be used! According to the PIX 
documentation the fixup protocol ftp statement is only supposed to affect 
incoming connections to the specified port so that the IP address passed 
back in response to active connections is replaced with the NAT'd address 
on the PIX.

Of the other suggestions, I think some of the followups answered them but 
I'll summarise.

Passive FTP is required from inside my PIX due to PAT - with active there 
is no way for the remote FTP server to open a connection back to my 
machine through the PIX even though WS_FTP is listening, as PAT doesn't 
allow any incoming connections due to having to map ports as well as IPs 
in a many to one for IP (outgoing) and many to many for ports.

"The most likely reason the passive ftp through the Pix is failing is a 
bug 
in the Pix code:  CSCdp09306, fixed in 5.0(2.212) and 5.1(1.208)."
As I stated in my original message I'm running 5.3(1) already, and 
successfully use passive ftp with other servers.


But after all this there is still something "interesting" about the config 
at the hosting provider. I've never had a problem like this before, and as 
I said I use FTP daily (actually about 20 times a day!) with our sister 
company that also uses Serv-U which is behind a PIX and PASV works fine. 
But I also need to use active connections and using "no fixup protocol ftp 
21" disables the use of active ftp. I'm going to try to "persuade" the 
hosting provider to send me a copy of their Serv-U config so I can see 
what's different between their setup and the one at our sister company.

Dan
---
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