Several people have suggested the possibility of using real-life reserved domain names. (For those curious, I have a summary of names and networks reserved for examples and documentation on my personal web site.)
Some people have even suggested using real-world domain names that are somehow undesirable, but still valid.
Yet others have suggested to register a domain name of your own, such that you are able to control its content.
I'm going to go out on a limb and suggest that there is a way to make up valid-looking domain names that actually will not exist.
That's because the two-letter top level domains are ISO 3166-1 alpha-2 country or territory codes. (ruakh pointed out in a comment that there exist exceptions to this rule. See below.)
Wikipedia has a handy table of assignment status of all such code combinations.
There are four ranges that are "free for assignment at the disposal of users" and thus, barring a major rework of the ISO standard, cannot possibly become valid top-level domains. Those are
AA (just that one),
ZZ (just that one).
The same Wikipedia article also has a short list of examples how some of these are currently being used. There are also a large number of codes reserved but not free for assignment for various reasons and varying lengths of time.
Basically, if you compose a domain name like you normally would on the Internet,
- but give it a top-level domain out of the ISO 3166-1 alpha-2 "free for assignment at the disposal of users" range, then you can be all but certain that it will not clash with any real-world Internet domain name now or in the future.
- but use any of the other ISO 3166-1 alpha-2 reserved combinations for a TLD, then you have to check to make sure that you aren't causing a potential name conflict (for example,
EU is "exceptionally reserved", and is actually available as a top-level domain), but for the most part you should be okay.
So it's perfectly possible for your character to have an email address like
firstname.lastname@example.org and you can be as certain as one can reasonably be that nobody will be registering the domain name
momandpopwebmail.qw for use on the actual Internet. (Maybe "QW" means "quickweb" in your world?)
Always ISO 3166-1 alpha-2?
As was pointed out by ruakh, citing
.uk as an example, there are a small number of country-code top-level domains that do not match the country's ISO 3166-1 alpha-2 country code, which in this case is
The criteria for eligibility for a two-letter ccTLD are laid out by the Internet Assigned Numbers Authority (IANA). There are a few other exceptional cases allowed for, but the main exception is for ccTLDs that do not match the country's alpha-2 code, but were originally approved before 2000 under an exceptional delegation in ISO 3166 and still maintain that status:
- Grandfathered prior to 2000. ICANN codified the rules under which future exceptionally reserved delegations may be considered in 2000 in Resolution 00.74. Certain domains were delegated on the basis of being “exceptionally reserved” by the ISO 3166 Maintenance Agency prior to this date. These domains were “.UK”, “.AC”, “.GG” and “.JE”. Of these, “.GG” and “.JE” are now listed in the ISO 3166-1 standard and therefore qualify normally. The remaining two domains that are grandfathered under their original eligibility are “.UK” and “.AC”.
It's worth noting in relation to ruakh's example of the United Kingdom that the Internet Corporation for Assigned Names and Numbers (ICANN) lists
.gb as "unassigned, reserved" and "originally meant to replace
.uk". We also note that Wikipedia's summary table lists both
UK as "exceptionally reserved".
Because the rule quoted above is about the eligibility of ccTLDs that were established before the current rules for ccTLD eligibility took effect in year 2000, barring an IANA rule change, no new ccTLDs can be assigned under the grandfathering criteria. While not exactly an ISO standard, these rules do on the Internet have status similar to that of an ISO standard.
Since none of the "free for assignment at the disposal of users" ISO 3166-1 alpha-2 codes fall under the grandfathering rule, and no other eligibility criteria appear to apply, we can still safely use those ranges confident in our assessment that they will not be assigned as top-level domains.
What about two-ASCII-letter TLDs not covered by ISO 3166-1 alpha-2?
This is covered by Internet Corporation for Assigned Names and Numbers (ICANN) Resolution 00.74, which states that (my emphasis):
It is therefore RESOLVED [00.74] that the IANA staff is advised that alpha-2 codes not on the ISO 3166-1 list are delegable as ccTLDs only in cases where the ISO 3166 Maintenance Agency, on its exceptional reservation list, has issued a reservation of the code that covers any application of ISO 3166-1 that needs a coded representation in the name of the country, territory, or area involved;
The "advised" is a bit of a red herring here; it means "we are telling you that", not "we are suggesting that". The operative part specifies that "alpha-2 codes not on the ISO 3166-1 list" can be assigned as ccTLDs only in the case that said code has a status of "exceptional reservation". As a consequence, the set of TLDs described by "alpha-2 codes" (two English alphabet characters) is restricted to the meaning that those character combinations have in ISO 3166-1 alpha-2.
But... but... what about in the future?
Sure, things can change. But at this level, things change very slowly. Given how many different entities likely use the "free for assignment at the disposal of users" ISO 3166-1 alpha-2 ranges for their internal use, were the relevant ISO committee to start to assign those codes for other uses, all hell would break loose. If these codes are ever to be assigned to any other use, there would likely be a decades-long transitionary period preceding it. Compare the current transitional reservations which in several cases stretch out to the 2050s, still a good 30-40 years into the future.
Also note that a good half or so of the alpha-2 codes are as of yet unassigned. Should a new country appear tomorrow that is sufficiently recognized to receive its own ISO 3166-1 alpha-2 code, it is likely that an appropriate two-letter code could be selected without needing to do anything with the ranges that are specifically available for users' own use.
We also note that the Frequently Asked Questions for the gTLD application process as published by the ICANN specifically states that (my emphasis)
2.12 Can a New gTLD name be 2 letters?
Applied-for gTLD strings in ASCII must be composed of three or more visually distinct characters. Two-character ASCII strings are not permitted, to avoid conflicting with current and future country-codes based on the ISO 3166-1 standard.
On the whole, I wouldn't worry about the risk of collions between future assigned TLDs and the "free for assignment at the disposal of users" ranges in ISO 3166-1 alpha-2. If it ever happens, your story might even become a bit of international relationships history.
- Use a two-letter top-level domain of