18. Except as otherwise provided by the Act, these Rules or any order —
(a)
all notices, summonses and other documents except those of which personal service is required, shall be deemed to be sufficiently served if left at or sent by prepaid post to the last known address of the person to be served therewith or to the address (if any) at which such person has authorised service on him to be effected; and the notice, summons or document if so sent by prepaid post shall be considered as served at the time that the same ought to be delivered in the ordinary course of post by the post office, and notwithstanding the same may be returned by the post office;
(b)
no service shall be deemed invalid by reason that the name, or any of the names other than the surname of the person to be served, has been omitted from the document containing the person’s name if the Court is satisfied that in other respects the service of the document has been sufficient; and
(c)
when the solicitor for a party to be served accepts service of a document on behalf of that party and indorses the original or a copy thereof to that effect, that service shall be deemed sufficient.