Pauline,
That @ by itself should work but MelbourneIT has had problems with IE browsers, specially IE9.
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It is best to use FireFox or Google's Chrome Browsers to perform this operation for IE9 has some formatting problems and sometimes there are problems with Adding TXT Records.
Pasted from www.builditon365.com/.../MoveOLSBdnTo365.aspx
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If you have Firefox or Chrome, use them to set the TXT record.
If that doesn't work - follow Maggie's advice "Contact MelbourneIT"