I’m assuming by “dot” you meant @
In fact both are optional. With FQDN-Adressing a user without domain defaults to localhost, with Bang-Adressing there is no @ because the last system is left for interpretation of the last receiver and if he consideres it a user, so be it.
I rooted my 2013 Samsung TV and overclocked it from 800 to 1200Mhz (the whole system is actually build for 1200Mhz but only the Highend-Ones are qualified for it). To my surprise the amount of data it send to Samsung was quite reasonable but still I removed most of it. Full removal of Internet is not an option because then I lose HbbTV and Prime TV which is like 50% of what I use that device for. And since I rooted it I also use it for BS and the public broadcasting mediatheks. Also, it now runs Quake2 in 1920x1080 in ~20fps.
try [email protected] or user@d.e.a.d.b.e.e.f.0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.1.2.3.4.ip6.arpa just for the giggles. Mix it with BANG-Adressing:
123.45.67.89.in-addr.arpa!d.e.a.d.b.e.e.f.0.1.2.3.4.5.6.7.8.9.a.b.c.d.e.f.0.0.0.0.1.2.3.4.ip6.arpa!user
No, dots are NOT necessary. Actually you do not even need to supply a domain or a top level domain because mails then default to the default system which is usually localhost.
But even for routed mail there doesn’t need to be a dot.
There is still valid Bang-Adressing for UUCP routed emails:
!bigsite!foovax!barbox!me
This is a valid email which basically means “send my email to bigsite, from there to foovax, then to barbox, to the user me.”
And if you are in a playful mood - mix FQDN and BANG addressing…
A couple of years ago I made Hotmail crash by sending a mail to googlemail.de!hotmail.com!googlemail.com!hotmail.de!googlemail.ca!hotmail.ca!googlemail.fr!hotmail.fr!.. [repeated it for 32kByte] …!myuseraccount - their server literally crashed completely all over the world for like 15 minutes. I am so proud of myself but then it was their fault for not complying to RfC822.
That is just hilarious but also…
I just remembered that Bram Moolenaar, the author of vim has recently died…
He was a real good person. Back when he released his first vim for Amiga Computers I exchanged some emails with him and he handled even my less smart suggestions very professional.
I just take the chance to remind everyone to spend some money for his Uganda Charity.
In my whole life I never bought digital audio or video content on vinyl, VHS, CD, DVD, Blueray. Never ever. It sounds as weird to me like paying for air to breath.
But one day I visited a live concert of a small band which I loved as a teenager. After the show I met with their drummer, gave him €200 cash and said “You know, when I was young you were cool about kids copying your music without paying. You told us if we like you music we can enjoy it. And if we can afford it, we can pay you. Back then I couldn’t. Today I can.”
And so I paid them five times as much as I saved back then by copying their music.