Hostname vs FQDN

[mwelzl]

From the review by Paul Wouters, DISCUSS part:

Can WithHostname be unqualified? (God I hope not!)
If not, can the call WithHostname be renamed to WithFQDN ?
If it can be unqualified, how does one deal with credentials
and identifiers, eg with a 'search domain' containing multiple
domains, RemoteSpecifier.WithHostname("mail") could end up on
either mail.example.com or mail.example.net (or heaven forbid,
the .mail TLD)

[mwelzl]

Should be a comment in the implementation draft (hostname is expected to be a FQDN).
In API: applications SHOULD pass FQDNs.