SharePoint Online Extranet Users limitation

[unnie ayilliath]

I am trying to set up an extranet on SharePoint Online. I have around 50,000 external users who needs to be added as external users (Guest accounts) into our tenant. My tenant has around 3000 E3 license users.  The SharePoint Online limits document says the below thing:

"Note: There is no limit to the number of external users you can invite to your SharePoint Online site collections." Source

Now, Azure AD B2B collaboration licensing guidance document says that for each licensed user we can invite upto 5 guest users who can use same features as the licensed user (1:5 ratio).

" A customer wants to invite 100 B2B collaboration users to its Azure AD tenant. The customer assigns access management and provisioning for all users, but 50 users also require MFA and conditional access. This customer must purchase 10 Azure AD Basic licenses and 10 Azure AD Premium P1 licenses to cover these B2B users correctly. If the customer plans to use Identity Protection features with B2B users, they must have Azure AD Premium P2 licenses to cover the invited users in the same 5:1 ratio" Source

Does this Azure AD B2B Collaboration limit apply to SharePoint also (since external users are guest users in Azure AD)?

Can I add 50k external users to SharePoint Online without purchasing any additional licenses to meet the 1:5 ratio?

[#2]

Well, it seems that if you use Azure B2B you will need additional licenses...but if you add those external users directly to SPO, you won't need those additional licenses

[#3]

What do others SharePoint experts follow? Should we even worry about number of external users added? Also, since site owners can add external users themselves it will be difficult to keep track of this.

[#4]

Azure B2B does not require SPO licensing. Azure B2B is in effect the same as SPOs sharing functionality; SPO is just using an older methodology.

You'll see that when you invite someone to an SPO resource, they're added to your tenant just like an Azure B2B user would be.

[#5]

Thanks @Trevor Seward

"You'll see that when you invite someone to an SPO resource, they're added to your tenant just like an Azure B2B user would be"

So, does Azure B2B licensing limit (5 guest accounts per licensed account ) regarding external collaboration apply to SharePoint Online?

I want to add 50k external users to my tenant (3,000 E3 licenses) through SPO external sharing, so is there any licensing limits I should be considering?

[#6]

Your best bet to get this answered officially is to contact your Microsoft TAM or partner who you purchased O365 licensing from.

[#7]

@Trevor Seward @Juan Carlos González Martín Sadly, we are waiting for more than 6 months to get a concrete answer for this question from Microsoft regarding this. So thought to reach out to the community on the same :( 

[#8 · Accepted solution]

Got response from Microsoft. We can have unlimited number of external guest users thru SPO external sharing. The 1:5 limitation mentioned in Azure B2B collaboration does not apply in this case.

See MS answer in the Github issue: https://github.com/MicrosoftDocs/azure-docs/issues/8564#issuecomment-444918954