New Outlook: Fix Custom Dictionary
Outlook
Nov 25, 2025 5:18 PM

New Outlook: Fix Custom Dictionary

by HubSite 365 about TRACCreations4E

My channel covers training videos of Microsoft 365 Online and Desktop products like Outlook, Excel, Word, PowerPoint, and Microsoft Teams. Microsoft's classic products are evolving with modern technol

Microsoft pro tip: sync New Outlook custom dictionary with Classic Outlook and Word RoamingCustom.dic to fix spell check

Key insights

  • New Outlook and Classic Outlook use different dictionary files, so words you added in Classic may not appear in the new app.
    The new interface currently reads a different dictionary location, which is why custom words can seem missing.
  • The Personal Dictionary menu in New Outlook only shows words added inside that app, not all system or legacy entries.
    Check other dictionary files to see the full set of saved words.
  • Locate and inspect your old CUSTOM.DIC file from Classic Outlook to recover saved words.
    Open it with a text editor to view and copy the word list if needed.
  • Make RoamingCustom.dic the default dictionary in Word so Office apps share the same custom words.
    In Word: File > Options > Proofing > Custom Dictionaries, add or select RoamingCustom.dic and set it as default, then restart Word and Outlook.
  • Use the Windows Personal Dictionary or add words in Word to ensure spelling is consistent across Microsoft 365 apps.
    Adding words at the system or Word level keeps them available to Outlook (new and classic) and other Office programs.
  • Classic Outlook users should perform this one-time step: copy entries from CUSTOM.DIC into RoamingCustom.dic, then set RoamingCustom.dic as the default and restart apps.
    After that, add new words in Word or the Windows personal dictionary so they sync properly with New Outlook.

Video Overview and Purpose

The YouTube video by TRACCreations4E addresses a common annoyance for Microsoft 365 users: the new Outlook interface not recognizing words saved in a personal custom dictionary. The creator explains why the issue appears after switching from the legacy interface and offers a clear, fast fix that restores consistent spell checking across apps. In addition, the video walks viewers through the one-time steps needed to keep custom words available in both Classic and New Outlook. Consequently, the tutorial targets anyone who relies on a personalized dictionary to reduce false spell-check flags.


Why the Problem Happens

As the video describes, the root cause lies in how the two Outlook versions use different dictionary files and settings. Specifically, Classic Outlook often writes to a file named CUSTOM.DIC, while the New Outlook and modern Office apps may reference a different roaming file such as RoamingCustom.dic. Therefore, when users switch to the New Outlook, their previously added words can appear missing because the app is pointing to a different dictionary location or an unlinked profile.


The Fix Demonstrated

TRACCreations4E demonstrates a straightforward sequence: locate the old CUSTOM.DIC, verify its contents, and set RoamingCustom.dic as the default dictionary in Word so that Office apps use the same word list. First, the presenter shows how to open the Classic dictionary file and confirm personal entries. Then, the video walks viewers through the Word options where you can set the default personal dictionary file, which propagates to Outlook when Office apps share that setting.


Step-by-Step Action and One-Time Tasks

Importantly, the tutorial emphasizes a one-time migration step for Classic Outlook users who have accumulated many custom entries. After copying or pointing Word to the roaming dictionary file, users must ensure that Office sync or roaming settings are active so the RoamingCustom.dic travels with the user’s profile. Moreover, the presenter suggests opening Word and a modern Outlook instance afterward to confirm that the new dictionary is recognized and that spelling checks behave consistently across apps.


Tradeoffs and Practical Challenges

While the method restores consistency, it carries tradeoffs. For example, relying on a roaming dictionary is convenient for users who work across multiple devices, but it depends on profile sync and correct Office account sign-in. If syncing fails, the roaming dictionary may not update in all locations, which reintroduces inconsistency. Thus, although the fix removes most friction, it also requires users to manage account settings and understand where their dictionary lives.


Recommendations and Takeaways

For most users, the clear takeaway is to consolidate custom words into the file that new Outlook uses by default and to verify roaming or sync settings within Microsoft 365. In practice, this involves a short manual step followed by a verification check across Word and Outlook; however, administrators should note that enterprise policies or profile redirection can complicate the process. Ultimately, the video delivers a practical balance: it offers a fast, repeatable solution while warning that some environments will need extra attention to syncing and permissions.


Conclusion

TRACCreations4E’s tutorial provides a concise and usable approach to a frustrating gap between legacy and modern Outlook experiences. Moreover, it explains the technical difference in dictionary files and gives a clear path to unify custom words so users regain reliable spell checking. Therefore, users who depend on industry-specific jargon or names should follow the one-time migration steps and confirm roaming is active to avoid future problems. In summary, the video turns a confusing behavior into an actionable fix that most readers can perform in minutes.


Outlook - New Outlook: Fix Custom Dictionary

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