Back in the bad old days some ISP's limited the number of email accounts you could have but I have always been able to have enough accounts for each member of the family. These days most will allow you to create multiple accounts I am sure even BT do not limit you to one email address.
It may well fail in cases where split domain routing is at play (commonly used when migrating users between platforms). There the MX record points at the new host, however on receipt of mail it may fail to resolve the user, however rather than hard fail at that point, it again forwards to the next handler in the chain - typically the old mail host.
GMX - I've been using them for about 5 years now. No spam (literally, not one in the 5 years-odd I've been using this NG address), good choice of names (because nobody else uses them), clear web page access, and reliable.
One of my Xmas jobs is to move my 21 year old hotmail account into one I own the domain of, and arrange to collect my mail directly.
Certainly Hotmail - despite being told to not spam-check mail - spam checks mail (badly) and things end up in "Junk" before my mail client (Evolution) can get to them.
It's irritating, as having an account which is <myname>@hotmail.com was a subtle way of pointing out how much experience I have. But that said, owning the domain <myname>.com is a good substitute. With <myname>.eu as a nice garnish :)
The moment gmail was mandated (plus a Google+ "account") for access to the Playstore, was the moment I decided to never use it except for Google stuff. Currently it's still obeying my "forward everything to hotmail" rule.
Which begs the question: What's in it for them ? I'm guessing irrespective of privacy laws, they are busily scanning emails for keywords to sell onto the "big data" fetishists.
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