File uploader
What Should You Check When Unable to Attach Files in Outlook?
When trying to send an email in Outlook, there may be instances where files cannot be attached, or errors such as "Attachment failed" or "This file cannot be attached" are displayed.
The causes are varied, including file size limits, dangerous file extension restrictions, issues with Outlook itself, and the impact of add-ins.
First, check the following items in order.
- Is the file size not too large?
- Is it not a prohibited file extension?
- Is Outlook or Office up to date?
- Is an add-in causing any issues?
- Does the same symptom occur in the web version of Outlook?
- Is the attached file itself not corrupted?
The Most Common Cause is Exceeding the File Size Limit
According to Microsoft support information, Outlook has restrictions on the attachable size depending on the type of email account or administrator settings. Generally, around 20MB to 25MB is a common guideline.
Attaching multiple photos, videos, or PDFs can easily exceed this limit.
Particularly high-resolution photos or videos taken with smartphones can be quite large, so caution is needed.
If size is the issue, the following methods are effective.
- Compress it into a ZIP file
- Reduce image size
- Delete unnecessary files
- Use a file sharing service
There are Prohibited File Extensions in Outlook
Outlook imposes restrictions on certain file extensions to enhance security.
Examples include the following.
- .exe
- .bat
- .cmd
- .js
- .reg
- .vbs
- .ps1
These files can be easily misused for malware distribution, so they are blocked by default.
If you must send them, compressing them into a ZIP file is an effective method. Microsoft also recommends creating compressed files.
If Unable to Attach via Drag & Drop
There may be cases where files do not get attached even when dragged and dropped into the email window.
In such cases, please try selecting directly from the "Attach File" button.
Also, drag and drop may not function properly between Outlook started with administrator privileges and Explorer under normal privileges.
Restarting Outlook may also resolve the issue.
Add-ins Can Also Be the Cause
Add-ins for PDF software, security software, etc., can affect Outlook’s ability to attach files.
If you suddenly cannot attach files, try starting Outlook in safe mode to check.
- Windows key + R
- Type outlook.exe /safe
- Press Enter
If you can attach files normally in safe mode, the add-in is likely the cause.
Try the Web Version of Outlook
To determine whether the issue is only occurring in the desktop version, try the browser version of Outlook as well.
If you can attach files normally in the web version, there may be issues with Outlook's settings, cache, or add-ins.
Conversely, if you cannot attach files in the web version either, it may be due to account settings or organizational policies.
For Large Files, Shared Links are More Convenient
When sending videos or large numbers of photos, email attachment is not suitable.
In such cases, using a file uploader to send a shared link is convenient.
With UploadF, it can be accessed from both PC and smartphone, and files can be easily uploaded with drag and drop.
- Free to use
- No membership registration required
- Password protection available
- Choose a storage duration
- Supports simultaneous upload of 100 files
Without being troubled by Outlook's attachment size limits, you can simply paste the shared URL in the email body to send files to others.
Convenient Features Before Sending Image Files
When sending images, you can also take advantage of the image-related tools available in UploadF.
- Online image editing
- Background transparency
- Mosaic processing
- OCR text recognition
- Color code extraction
- AI image learning prevention tools
By adjusting the image size before sending, you can also help mitigate attachment size issues with emails.
Summary of Inability to Attach Files in Outlook
When unable to attach files in Outlook, first check the file size and extensions.
Then, by sequentially ruling out issues with add-ins, Outlook itself, and organizational security settings, many problems can be resolved.
Especially if the goal is to send large files, utilizing file-sharing services may be more efficient than sticking to email attachments.
If you want to share easily without worrying about size limits, consider using a free file uploader like UploadF as one of the options.