While entering some dummy data into some code for testing, I got to thinking about the 555 fictitious phone number in the US and whether or not there is an equivalent value for email and domain names.
It turns out that IANA has reserved the domain example.com and the top level domain .example for fictitious purposes.
It also turns out that numbers beginning with 555 do actually exists in many cases. The only reserved range (within all US area codes) is 555-01xx. Also, in plenty of other places in the world, 555 is a perfectly working prefix. There really isn’t a single value you can use that is guaranteed.
Thus, for fictitious phone and email , the first value I’m going to use are 818-555-0123 and jdoe@example.com