One of the challenges of logging in to Blogger or Google involves account names and passwords, that may be shared with an email account that is the basis for the Blogger / Google account name.
Non GMail based Blogger / Google accounts initially share an account name / email address with the source non GMail email account. If you change a non GMail email address, the Blogger account name will not change. If you delete a non GMail account, the Blogger account is not deleted. Finally, even with shared account names, the passwords between the email account, and the Blogger / Google account, are not automatically shared.
With a GMail / Google based Blogger account, on the other hand, both the account name and password will be shared - since it's the same account. If you delete a GMail / Google Blogger account, the Blogger account - and all owned blogs - are also deleted.
Besides the account name / password confusion, use of the Google login wizard is complicated by use of Google Apps based email accounts.
Use of the new Google login wizard is a challenge because of the blind login process - and the lack of detailed diagnostics, when an incorrect account name or password is entered. The lack of detailed diagnostics helps prevent hacking of our Google accounts, when our email address and various personal details become known to the public. Any mistakes result in one monolithic error.
The email or password you entered is incorrect.
Google Apps based email accounts are a frequent concern, when frustrated custom domain owners need to access their Google Apps accounts, to either update domain registration payment details, or to access the registrars domain management dashboard.
Google Apps access, which uses the Google multi-account login wizard, is complicated by domain owners who do not realise (or remember) the non GMail based Google Apps account name - or the password.
Before Google Apps based email domains became an issue, it was possible to easily identify non GMail based Blogger / Google accounts, as opposed to GMail based accounts, based on one significant detail - the absence of "gmail.com" / "googlemail.com" in the account name.
Observing that a given Blogger account name did not include "gmail.com" / "googlemail.com", we could advise a Blogger account owner of the issues involving account name / password sharing, between the source email account, and the Blogger / Google account.
Thanks to the existence of Google Apps based email domains, it is now possible to have GMail / Google accounts which lack the "gmail.com" / "googlemail.com" in the account name - and we see the confusion.
- Some blog owners may delete an unused "non GMail" Google account, not realising that they are deleting the necessary Blogger / Google account that owns a given blog.
- Other blog owners may be unable to use the Google login wizard effectively, since they don't understand that a non "GMail.com" account may be a Google account.
- And, in truly unfortunate scenarios, we have blog owners who lose control of their blogs when their employer, Internet Service Provider, or school converts their domain to use Google apps management
Just as it's impossible to canonically identify "legacy" accounts, it's a challenge to adequately describe the issues specific to Google Apps based non "GMail.com" Blogger / Google accounts. Control and synchronisation issues, relevant to both the account names and passwords, will always cause confusion, to Blogger blog owners.
Articles about regaining account control - and proper use of the new Google One Login wizard - will be referenced frequently, in Blogger Help Forum: Something Is Broken.