Local part of e-mail address no longer accepts numbers at the start
I used to have "8.bit" as an alias on my Premium Outlook package associated to my domain managed here: https://premium.outlook.com/#/ManageAliasV2
I deleted the alias as I was at my maximum to re-add it as "8bit" but there was no on screen message to confirm/deny the request so I reverted to "8.bit" as I had previously, but this too failed to add.
Looking at the console feedback, it seems e-mail aliases beginning with a number are raising 500 server errors.
"API failed; URL: https://premiumapi.outlook.com/v1/aliases/8bit?isDefaultFromAddress=false& Action: PUT Status: 500 Error Message: 0x80048102-1an internal error was encountered, check the soap fault for detailed information
0x80041103the signin name is incomplete or has invalid characters.
Having the number at the end of the alias works, so "bit8" or "bit.8".
Looking at the RFC spec for the local part of an e-mail address, I don't see any issue with an e-mail address starting with a number, and I have other e-mail addresses set up on other providers which allow this.
Is this an unintentional error (which I hope it is as there's no response on screen of invalid characters which I can raise when using known illegal characters) or a new restriction on what an alias can be?