From rfc 3986: > The rightmost domain label of a fully qualified domain name in DNS may be followed by a single "." and should be if it is necessary to disting

From rfc 3986: > The rightmost domain label of a fully qualified domain name in DNS may be followed by a single "." and should be if it is necessary to distinguish between the complete domain name and some local domain. When there is no ambiguity then they mean the same thing. Anyway, as a sibling comment said, it's not a good rfc to use for this purpose.