How is .tel different from other domains?
What's a NAPTR record? What are the key benefits of a NAPTR record?
You can also label each NAPTR record, for example the phone number could be labeled “my home”. Another key benefit of NAPTR records is their extensibility. New NAPTR types can be created as new means of communications are developed, making the .tel solution a very powerful long-term communications hub. The full definition of a NAPTR record, in the Wiki.
Do I need to understand DNS to use the .tel platform?
What DNS server software am I restricted to use?
If your DNS server is relatively up-to-date (within the past few years), it supports EDNS0. If your DNS server is older than that, you probably have major security holes that need patching!