SharePoint Online sites are great for organizations to share information with external users. The issue with this is that Microsoft requires that a Microsoft Account is used to access SharePoint site. This is not an issue if the external users have a Microsoft Account either through their Office 365 access (Organizational Account) or a personal Microsoft account the is used for other Microsoft services, such as OneDrive, Xbox, or Outlook.com.
Else a Microsoft account that uses the external email address will need to be created to get access to the SharePoint site. Below are the steps needed to create that account.
Note: Since Microsoft may change the process, these instructions are current as of December 2016.
1. Get the email invitation from the SharePoint site, click on the invite link (the text following Go To…).
2a. If you have a Microsoft or Office365 account, click the appropriate icon, and sign on to the SharePoint site. (one of the Red arrow options pictured below).
Skip down to step 6, Access to SharePoint Site.
2b. If you do not have a Microsoft type of account, you will need to create one.
Click on the “Create a Microsoft account,…” link, the red box in the picture above.
3. Enter the email address that the invitation email was sent to (i.e. @gmail.com).
Select a password.
It is highly recommended that this not be the same password as your email account access. This password would be used to access the SharePoint site.
Click the Next button.
4. Check your email account for a confirmation code that should have been sent from Microsoft confirming that it is your email account that is being registered.
Enter that code into the space provided then click the Next button.
5. The next screen should then be at a confirmation of your information.
If the information looks good, click the Looks good! button to continue.
6. You now have a Microsoft Account created using your non-Microsoft email address.
You should then be sent to the SharePoint site.
Use this account logon information to logon to the site in the future.
These steps create a Microsoft account that uses a non-Microsoft email account (either personal or via Office 365). This account could be used any time you need accessing any Microsoft Services that requires a Microsoft account, such as accessing other SharePoint sites, Xbox Live or other Microsoft online services.
This is a different account from your email access and it only uses your email address as a username. It is highly recommended that the password for this account not be the same as your email access account.