[IMail Forum] Notation conversion

[MIke Mckay]

Being a complete novice I realise this is probably a stupid question but here goes.   What is the correct dotted notation for the following what I think it should be is in brackets but a few of the online subnet calculators say it is incorrect for a class C, but this is all my isp has given me and IMAIL will not accept /xx notation,   212.1.128.0/19        (255.255.224.0) 212.157.128.0/18    (255.255.192.0) 212.159.128.0/17    (255.255.128.0)   but as it is subnetted in the 3rd octet shouldn't they all be shown as XXX.XXX.0.0 ?   Many thanks   Mike