On 11/20/21 05:47, russellbell--- via Exim-users wrote:
> 'They can not have MX records.'
> Why not? If an SMTP server at the address handles mail...
If, let's say, a new top level domain (TLD) is created which is numerical, and of a value in the range of 0..255, say 128. for example, then you can register a numerical label below it.
You can then construct a domain name such as 128.128.128.128. It would not be an IP address. It is a domain name.
In your zone file you can put:
departmentofsilliness.gedalya.net. 3600 MX 10 mail.gedalya.net.
or, if a numerical TLD existed:
128.128.128.128. 3600 MX 10 mail.gedalya.net.
But no one will look it up if they were treating it as an IP address. It only makes sense to look up DNS things in DNS. If you're looking up an MX record for 128.128.128.128 then by definition it is not an IP address.
Now, of course a numeric TLD is not allowed, exactly because you want code to be able to easily guess if a string should be treated as an IP address, or a domain name that needs to be resolved to an IP address.
> 'If there is any domain name that has an A record pointing to
> 123.456.789.012, it is likely to work much more often than using the
> IP address directly, even if it has no MX record.'
> There is an A record, but there's also an MX record that
> points to our mail server, a Microsoft Outlook thing: mail sent to it
> won't arrive at the target server.
There is an MX record - for what domain?
If there is an A record like your.mail.server. then fred@??? can be made to work, by configuring your.mail.server. as a local domain in exim.
if a.b.c. has an MX record pointing to your mail server, that is:
a.b.c. 3600 MX 10 your.mail.server.
then fred@??? can be made to work as well.
It sounds like you won't really need to worry about IP literals.
