If your email won’t send attachments, the message itself may be fine. The problem is often the file attached to it, the size of the message, the type of file, or the mail server rejecting it before it leaves your device.
This can be especially frustrating because normal emails may still send without any trouble. As soon as you add a photo, PDF, ZIP file, spreadsheet, or large document, the email gets stuck, fails, or disappears into the Outbox.
If the issue is part of a broader sending problem, my main emails not sending page covers Outlook, Gmail, Apple Mail, phone email, and business email problems too.
Why Attachments Can Stop an Email Sending
Email attachments add extra complexity. Your email app has to upload the file, your account provider has to accept it, the sending server has to process it, and the recipient’s server has to allow it.
A failure at any of those points can stop the message from sending.
- 📎 The attachment may be too large for your email provider.
- 🚫 The file type may be blocked for security reasons.
- 🐢 The upload may be timing out on a slow or unstable connection.
- 📤 The message may be stuck in the Outbox and blocking other emails.
- ⚙️ The email app may be mishandling the attachment or account settings.
Large Attachments Are a Common Cause
One of the most common reasons an email won’t send attachments is file size. Photos, scanned documents, videos, design files, and exported PDFs can become much larger than expected.
Even if the file looks small on screen, the actual file size may be too large for email. This is especially common with:
- 📷 High-resolution phone photos.
- 📄 Scanned PDF documents.
- 🎥 Video files.
- 🧾 Large invoice or report packs.
- 🗂️ ZIP files containing many documents.
When the attachment is too large, the email may sit in the Outbox, fail with an error, or appear to send forever without completing.
Outlook Large Attachment Problems
Outlook can be particularly confusing when a large attachment causes problems. The message may sit in the Outbox and keep trying to send, even after you realise the attachment is the issue.
Sometimes Outlook then refuses to send other messages until the stuck email is removed or fixed.
Common Outlook large attachment symptoms include:
- 📤 An email stuck in the Outbox with a large attachment.
- ⏳ Outlook repeatedly showing “sending” but never finishing.
- ⚠️ Send/Receive errors after attaching a file.
- 🔁 The same message trying to send every time Outlook opens.
- 📎 Other emails failing because one bad message is blocking the queue.
In many cases, the fix is not just to keep pressing Send. The stuck message needs to be dealt with safely so it does not keep blocking the mailbox.
If the message is now trapped in the Outbox, my article on email stuck in Outbox explains that specific problem.
Gmail Attachment Not Sending
Gmail attachment problems can look different depending on whether you are using Gmail in a web browser, the Gmail app on a phone, or an email app connected to a Gmail account.
In Gmail, attachment sending can fail because the file is too large, the upload stalls, the browser session has expired, or the Gmail app is not syncing properly.
Typical signs include:
- 📎 The attachment upload never completes.
- 📱 A message gets stuck sending from a phone.
- 🔐 Gmail asks you to sign in again or refresh the session.
- ☁️ The file needs to be sent as a cloud link instead of a normal attachment.
- 🚫 The file type is blocked or rejected.
If Gmail is failing more generally, my article on Gmail not sending emails covers phone, app, and web issues.
Sometimes the best solution is to send a link to the file rather than attach the file directly, especially for large photos, videos, or document packs.
Some File Types Are Blocked
Email providers often block certain file types because they can be used to spread malware or unsafe scripts. This can happen even when the file is legitimate.
Blocked files may include executable files, scripts, compressed folders, or files that contain risky content inside them.
- 🧩 Installer files may be rejected.
- 🗜️ ZIP files may be blocked if they contain unsafe file types.
- 📜 Script files may be stopped by the sending or receiving server.
- 🛡️ Security filters may block attachments before the recipient sees them.
Renaming a blocked file to trick the email system is usually a bad idea. It may still be detected, and it can look suspicious to the recipient. A safer option is often to use a proper file-sharing link or another approved transfer method.
The Recipient’s Mail Server May Reject the Message
If this is happening with quotes, invoices, or business documents, see my article on business email not sending.
Sometimes the email leaves your device but is rejected by the recipient’s mail server. This is common with business email systems, schools, government departments, medical practices, and larger organisations with strict filtering.
The rejection may happen because of file size, file type, security policy, spam filtering, or the way the message is formatted.
When this happens, you may receive a bounce-back message. That message often contains the clue, but the wording can be technical and hard to interpret.
Slow or Stalled Sending Can Be an Upload Problem
Sending an attachment requires uploading the file first. If your internet connection is slow, unstable, or under load, the message may appear to be stuck even though the email account is otherwise working.
This is more likely when sending from:
- 📶 Weak Wi-Fi.
- 📱 Mobile data with poor reception.
- 🏠 A home internet connection with low upload speed.
- 🧳 Hotel, airport, or public Wi-Fi.
- 💻 A computer running cloud backups or other uploads in the background.
In these cases, the attachment may eventually send, but it can also time out and fail partway through.
What You Can Try First
Before changing account settings, it is worth checking the simple causes first.
- 📏 Check the file size before sending.
- 🧪 Try sending a plain test email with no attachment.
- 📎 Try a much smaller attachment to see if the problem is size-related.
- 🔄 Restart the email app or browser and try again.
- ☁️ Use a cloud link for large files instead of attaching them directly.
- 📤 Check whether one stuck Outbox message is blocking everything else.
If a small test attachment sends but the original file does not, the problem is probably related to the file size, file type, or content of the attachment.
When It Needs Proper Troubleshooting
If attachments keep failing, the real cause needs to be narrowed down. The fix depends on where the failure is happening.
I usually check whether the issue is with the file, the email app, the account, the device, the internet connection, or the mail server. For business email, I may also need to check server limits, security filtering, and bounce-back messages.
This matters because the wrong fix can waste time. Reinstalling Outlook will not solve a recipient server rejecting a blocked attachment. Changing passwords will not fix a file that is too large. Compressing a file will not help if the account is stuck in an authentication loop.
Local Help With Email Attachment Problems
PcRiot helps home users and small businesses in Perth with email problems, including emails that will not send attachments, Outlook large attachment problems, Gmail attachment issues, and business mail server rejections.
I can help identify whether the problem is caused by the attachment, the email app, the account, the device, or the mail server, then fix the issue or recommend the right workaround.
If you need help with this, contact PcRiot for local support in Perth.