piatkow - 10:01 am on Oct 24, 2010 (gmt 0)
I live in the UK, however I would expect the legal position to be more or less the same.
IIRC if you send by Royal Mail the law assumes delivery if you have proof of posting (certainly the case when HMG posts something important to you). I don't know if other countries' legal systems regard their postal services as equally infallable.
Of course in practice we replace and claim back against Royal Mail.