Troubleshooting the ‘This is not a valid file name’ Error in Outlook: Free Guide

Published On - December 13, 2024 by Nasir Khan | Reading Time: 5 minutes

You might have faced errors like “This is not a valid file name” while sending an email in Microsoft Outlook. Such errors generally occur due to special characters in the name of an attachment file or invalid paths of files. Also, these issues hinder your workflow and delay important communications. Therefore, to help you out here is a blog discussing the error’s reasons and providing you with some easy and effective solutions. From free manual methods to using a reliable PST Converter Tool, you will find the answer here. Let us begin with knowing the error.

About- This is not Valid File Name Error in Outlook

This error 5152 message in Outlook is encountered when you try to save, attach, or open a file whose name is not valid (as per Outlook). A typical example of these characters includes unsupported characters, incorrect file paths, or problems with permissions. Well, it may block you from completing some very important tasks, such as sending attached files with emails. Moreover, it prevents you from accessing files in your mailbox. So, it’s important to fix this as soon as possible. But before that, it is important to find out the real cause behind it.

What Causes “Error 5152 This is Not a Valid File Name” in Outlook?

Before you get a perfect troubleshooting solution, it’s very important to know what factors may cause such errors. This will save your time and risk of data loss as well. The following are the reasons:

• The use of special characters such as \\, /, :, <, > in the file name is not supported by Outlook.
• When a file is moved, renamed, or located in a restricted folder, it produces an invalid file path, causing the error.
• Conflicting or incompatible add-ins can disrupt the entire functionality of Outlook.
• Any problem, corruption, or damage in your Outlook offline data file (OST) can also be the cause.
• Also, long file names or file paths exceeding 255 characters might cause compatibility issues.

Further, keeping this in mind, let us move forward to resolve the Outlook error ‘this is not a valid file name’.

How to Fix Not a Valid File Name Error in Outlook?

After knowing the causes, here are the solutions you need. These are based on different reasons. Choose the perfect match as per your Outlook performance.

#1. Rename the File Showing Error

As stated, the use of invalid special characters in file names can majorly lead to the Outlook error “This is not a valid file name”. Hence, to fix the issue, you need to rename the file by eliminating unsupported characters. Here are the steps to rename the error-detected file:

1. Firstly, identify and locate the file you need to attach or save.
2. Then, check for the special characters like <, >, /, \, |, : in the file name. Remove them.
3. Also, make sure the file name is concise and avoid using any unnecessary symbols.
4. At last, reattach or save the file. Try resending the email with that file again.

If the email is sent, your error is resolved.

Additional Tip: Make sure the file names are under 255 characters, otherwise it may cause compatibility issues again.

#2. Verify the File Path

Wondering why you need to verify the file path? Well, sometimes the reasons could be moving, deletion, or re-location of files in a restricted folder. This results in an invalid file path. For that, cross-check the file path using the following steps:

1. Browse and find out the file’s location in your system’s File Explorer.
2. Check if the file you need to send is present and accessible. Is it?
3. Your file may be located in a deeply nested folder. In that case, relocate the file to a simpler path like C:\Documents.
4. Finally, try to reattach the file to your emails and send it. Outlook won’t show the error again.

Additional Tip: Shorten the folder names and make it easy to find files. This can help you resolve the error 5152 this is not a valid file name.

#3. Disable Conflicting or Faulty Add-Ins

There are cases often where Outlook functionality is interfered with due to any incompatible or outdated add-ins. You should not neglect such conditions to prevent the ‘this is not valid file name error’. To find and disable faulty add-ins, the following are the steps:

1. Firstly, properly shut down your MS Outlook application.
2. To find faulty add-ins, run MS Outlook in Safe Mode: Press Win + R and type Outlook /safe. Tap on Enter.
3. After that, open Outlook, go to File > choose Options > Add-ins.
4. Under Manage COM Add-ins, click on the Go button.
5. A list of add-ins will be displayed. Uncheck all of them and click OK.
6. Once you have performed the steps above, restart Outlook. Re-try sending the email with the attached file.

Additional Tip: We recommend enabling one add-in at a time. So that you can identify the faulty add-in and prevent such errors in Outlook.

#4. Recreate the OST Data File

The OST file corruption may cause trouble in syncing and result in the “This is not a valid file name” error in the OST of Outlook. Therefore, rebuilding OST may resolve this problem. Follow the given steps to recreate the OST file:

1. First of all, ensure that Outlook is not running in the background.
2. Locate the default OST file: “C:\Users\\AppData\Local\Microsoft\Outlook\”.
3. Now, copy this OST file to a backup folder. Then, remove the original OST file.
4. Again, open the Outlook application. As soon as you open Outlook, it will recreate the OST file automatically. Followed by synchronizing your mailbox.

Additional Tip: You may find that some emails or folders are missing after recreating the OST file. Don’t Panic! Use a PST Converter Tool to recover lost Outlook data.

#5. Use MSRA to Resolve the Error

MSRA is short for Microsoft Support and Recovery Assistant. It is a troubleshooting tool designed by Microsoft to fix common Outlook errors like ‘this is not valid file name error’. This proficient utility automatically detects and resolves Outlook issues. Here is how to use MSRA:

1. Download the MSRA tool and install it.
2. Once you run the tool, you need to agree to the terms.
3. Afterward, select MS Outlook from the list. Click on Next.
4. Choose the Other Problems option. Later, follow the prompts as per MSRA to fix the error.

#6: Convert OST Files to PST

One of the most common reasons in case of such an error, can be OST file corruption. Well, if none of the above methods works, possibly your OST file is corrupted. Therefore, you can convert the OST file to PST and prevent losing valuable data anymore. A reliable tool like the Regain OST to PST Converter can easily recover and convert inaccessible OST files to PST format.

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Know how to use this professional tool:

1. Install the best OST to PST Converter on your system.
2. Run the tool and select the corrupted OST file.
3. Now, choose the saving folder and save the file as PST.
4. Lastly, use Outlook’s built-in feature Import/Export to import the PST file into Outlook.

Additional Benefit: The tool can recover orphaned OST files and export data directly to Microsoft 365.

Conclusion

The ‘This is not a valid file name’ error in Outlook can really cripple your workflow, but with the above solutions, you can easily get rid of the problem. From renaming files to recreating the OST file and using tools like MSRA, each method is carefully designed to target different causes of the error. Regain OST to PST Converter is the ultimate solution when dealing with corrupted OST files or missing mailbox items. Apart from solving the problem, it helps in keeping the data undamaged. Try these methods and send your emails without any hassle.