Updating ProxyAddresses, mine
From MyWiki
Set-ADUser -Identity <username> -Replace @{Proxyaddresses="SMTP=g.pompson@bold.ab.uk" Set-ADUser -Identity <username> -Add @{Proxyaddresses="smtp=bla01ff@bold.ab.uk"
When you use the Add, Remove, Replace and Clear parameters together, the operations will be performed in the following order: ..Remove ..Add ..Replace </scource>
