Infuriating "550 error report".  When I changed over from my Sierra Wireless to the new XT mobile broadband I somehow kept getting the 550 error message - able to send email to xtra.co.nz but no other email addresses.

I have resolved this after a lot of time...I could not find a simple answer anywhere so thought that I would post what I found - I appologise to all that know this one but I just couldn't find it in simple terms, so here we go:

Outlook
Tools
Account settings
Highlite email account and then click on change
POP3.xtra.co.nz
Send.xtra.co.nz
enter username and password
Tick:  Require Logon using Sucure Password Authentication (SPA)

Go to:
More settings
Outgoing Email Settings
Tick - My outgoing server SMTP requires authentication
Check - Use same settings as my incoming mail server

Go to:
Advanced
Incoming Pop3:  995
Tick: this server requires an encrypted connection (SSL)
Outgoing server SMTP: 465
Use following type of encrypted connection
Change in drop down menu to:  SSL

Down to Delivery:
Tick - Leave copy of message on this server  (This is advised - not needed)

OK
NEXT
FINISH

For all of those people who this works for I am really glad. I use Outlook and my ISP is Telecom Xtra.  Hope this helps.