Troubleshooting: SharePoint Invite Emails Not Coming Through (2026)

SharePoint invite emails not coming through is a frequent issue when sharing sites externally in Microsoft 365. When external users don’t receive invitation messages, even though SharePoint says “sent,” — the root cause is typically configuration, mailbox issues, or tenant external sharing policies. This guide explains why this happens and how to fix it.

Quick Diagnosis: SharePoint Invite Emails Not Coming Through (60-Second Check)

Before you dive deep, ask:

• Did the invite get created in Entra (Guest invitations), or did it die before that?
• Is the email stuck in Defender quarantine (yours or theirs)?
• Are you sharing to Everyone / Everyone except external users? If yes, no email is expected.
• Is the guest user already present in Entra ID → Users → Guest users? If yes, the invite was created — delivery is the issue, not SharePoint.
• Did the sender account have an active Exchange Online mailbox at the time of sharing? No mailbox = no invite email sent.
• Was the share done from a Team-connected SharePoint site or a private site collection? Policy behavior can differ.
• Is external sharing enabled at tenant level AND site level (not just one)?
• Is the recipient domain blocking Microsoft 365 system emails?
• Did you test with a different external email domain (Gmail/Outlook test)?
• Is conditional access blocking external guest redemption?
• Is the invite being triggered from a shared mailbox or service account? These often fail silently.
• Are sensitivity labels or Purview policies overriding sharing behavior?

Why SharePoint Invite Emails Fail Silently (Most Common Causes)

1) The sender doesn’t have a real mailbox (still the #1 gotcha)

If the person sending the invite has no Exchange Online mailbox / no valid email attribute, SharePoint may not send the invitation and won’t warn you. This was already noted in your current post and still happens.

Fix: Confirm the sender account has:

• A valid email address on the account
• An active mailbox capable of sending service notifications (Exchange Online)

2) You’re sharing to “Everyone” groups (expected behavior = no email)

If you share a resource to Everyone or Everyone except external users with “Send an email invitation” ticked, users won’t receive an email. Microsoft documents this as expected behavior.

Fix: Share to named users, not those broad groups, if you need an email invite trail.

3) Tenant/site external sharing settings block the invite

If external sharing is restricted at the tenant or site level, invitations can fail (or appear to succeed but never notify properly). Your current post mentions this; it’s still a major root cause.

Fix: Confirm external sharing is allowed at:

• M365 / SharePoint admin level
• Site level (site policy can be stricter than tenant)

4) Cross-tenant access settings block B2B collaboration (2026 reality)

Even when SharePoint sharing is enabled, the invite can be blocked by Entra cross-tenant access settings (common with enterprise partners). Microsoft calls this out in their B2B troubleshooting guidance.

Fix: Check Entra External ID / Cross-tenant access policies for B2B collaboration blocks.

5) Email security is quarantining or silently dropping the invite

In 2026, many orgs have stricter email filtering. Invitation emails can land in:

• Spam/Junk
• Quarantine (Defender)
• Or be silently rejected depending on policy and provider behavior

Microsoft’s quarantine documentation is the right place to verify and release blocked mail.

Fix: Check:

• Microsoft Defender Quarantine (admin + user views)
• Your outbound policies (if configured)
• Recipient’s mail admin allowlist (if corporate recipient)

One overlooked cause is sharing to broad built-in groups like Everyone or Everyone except external users. In this case, SharePoint may grant access but not send an invitation email. Microsoft documents this behavior clearly in their official sharing guidance.

How to Fix SharePoint Invite Emails Not Coming Through (9 Proven Fixes)

Fix 1 — Confirm the invite was actually generated

If the invite does not appear in Entra invitations/guest logs, it never left your tenant properly.

Fix 2 — Verify sender mailbox + licensing

Make sure the user sending the invite has a mailbox and can send M365 notifications.

Fix 3 — Stop sharing to “Everyone” groups when you expect email

No email is expected in that scenario. Share to named users instead.

Fix 4 — Check tenant + site sharing restrictions

If external sharing is limited/disabled, invites won’t reliably send.

Fix 5 — Validate cross-tenant access (partner org blocks)

Cross-tenant settings can explicitly block invites; resolve this with both org admins if needed.

Fix 6 — Check Defender Quarantine (yours and theirs)

Go to Quarantine and search for the recipient address / invite pattern; release if safe.

Fix 7 — Resend using Entra “Invite guest user”

If SharePoint UI invites are flaky, try sending via Entra guest invite flow (often behaves more predictably).

Fix 8 — Allowlist invite sender patterns if corporate recipients

Microsoft community guidance commonly suggests allowing the invite sender identity (varies by tenant).

Fix 9 — If deliverability is unreliable, send your own email with the sharing link

This is the 2026 “hard truth”: for some providers/policies, Microsoft-sent invitation emails can be unreliable, and the practical workaround is to generate the link and send from your own authenticated domain.

Best Practices for Reliable External Sharing (2026 Standard)

• Treat invite emails as best-effort, not guaranteed delivery in strict environments
• Prefer named-user sharing (clear audit trail, fewer edge cases)
• Maintain a “guest access playbook” (Entra cross-tenant + security + quarantine checks)
• Build governance around external collaboration so issues don’t recur (policy drift is real)

If this keeps happening across multiple sites, it’s usually a governance problem—consider a quick SharePoint consulting review to audit external access, policies, and guest lifecycle.

Frequently Asked Questions