Smart Email Clients — Source Index

Grouped by the four questions. ⭐ = official primary source (HubSpot KB / Microsoft Learn). Sources marked ✅ were independently fact-checked (3-vote verification). YouTube walkthroughs being gathered in a separate pass.

Part 1 — AI email clients (triage + HubSpot)

1. https://superhuman.com — Superhuman (AI client) ⭐
2. https://help.superhuman.com/Create-Your-Own-Split-Inbox — Split Inbox feature
3. https://help.superhuman.com/Organize-with-AI — AI auto-labels / auto-archive
4. https://efficient.app/best/ai-email-assistant — comparative review (Superhuman, Fyxer) ✅
5. https://techcrunch.com/2025/02/19 — Superhuman auto-archive coverage
6. https://clean.email/blog/ai-for-work/spark-mail-ai-review — Spark AI review

Part 2 — HubSpot's own email tools / extensions ⭐

7. https://knowledge.hubspot.com/connected-email/track-and-log-emails-with-the-hubspot-sales-office-365-add-in — Outlook add-in (logging + open/click tracking)
8. https://knowledge.hubspot.com/connected-email/track-and-log-emails-with-the-hubspot-sales-chrome-extension — Gmail Chrome extension
9. https://knowledge.hubspot.com/connected-email/how-to-install-hubspot-sales — install guide
10. https://knowledge.hubspot.com/connected-email/understand-hubspot-sales-email-open-and-click-tracking — how open/click tracking works

Part 3 — HubSpot BCC / forwarding logging ⭐

11. https://knowledge.hubspot.com/connected-email/log-email-in-your-crm-with-the-bcc-or-forwarding-address — BCC/forwarding mechanics, requirements, sender attribution (updated Apr 17, 2026)
12. https://knowledge.hubspot.com/articles/kcs_article/email/difference-between-bcc-and-forwarding — BCC vs forwarding

Part 4 — Outlook / Microsoft 365 repeated logout ✅ ⭐

13. https://learn.microsoft.com/en-us/troubleshoot/outlook/authentication/continually-prompts-password-office-365 — MS: continual password prompts ⭐
14. https://learn.microsoft.com/en-us/troubleshoot/outlook/sign-in/repeated-prompts-authentication — MS: repeated auth prompts ⭐
15. https://learn.microsoft.com/en-us/troubleshoot/microsoft-365-apps/office-suite-issues/another-account-already-signed-in — MS: conflicting accounts ⭐
16. https://learn.microsoft.com/troubleshoot/exchange/administration/modern-authentication-configuration — MS: force Modern Auth ⭐
17. https://learn.microsoft.com/entra/identity/conditional-access/concept-session-lifetime — MS: Conditional Access session lifetime ⭐
18. https://learn.microsoft.com/en-us/answers/questions/5851642/resolve-persistent-authentication-prompts-in-outlo — MS Q&A: remediation steps
19. https://coregptapps.com/blog/outlook-365-sign-in-loop-fix-cached-credentials — sign-in loop fix walkthrough
20. https://help.suitefiles.com/fix-constant-sign-in-prompt-for-office — credential-clear walkthrough
21. https://www.serverman.co.uk/software/microsoft/microsoft-outlook/outlook-password-prompt-loop/ — prompt-loop fixes

⚠️ Verification caveats (read before acting)

• Superhuman pricing/tiers are time-sensitive (post-acquisition restructure) — confirm at superhuman.com/plans before committing.
• Fyxer "unreliable drafts" rests on a single reviewer; trial before trusting.
• Some Part 4 fixes come from blogs/forums but are each corroborated by Microsoft Learn primary docs (the ⭐ links).
• Refuted during research (do NOT rely on): the "untick Always prompt for logon credentials" Security-tab toggle, and "clearing Credential Manager is the most common fix" framing — both voted down.

YouTube video walkthroughs [video]

22. Superhuman Tutorial 2026: Getting Started — features, shortcuts, AI triage walkthrough
23. Superhuman Email Review (2026) — months-of-use review + confirmed pricing ($30/$40 per seat/mo)
24. Fix Outlook Desktop Sign-In Loop (2026) — clear credentials, EnableADAL registry, update Outlook
25. Quick Fix: Microsoft Keeps Asking for Password (Outlook & Teams) — sign out/in, clear Credential Manager, Quick Repair
26. Stop Outlook Repeatedly Asking for Password 2026 — refresh credentials + "Always prompt" Security-tab toggle