If your emails are not sending, the issue can be caused by anything from incorrect email settings to attachment size limits or server-related problems. In many cases, the exact cause depends on whether the message is failing before it leaves your mailbox or whether it is being sent and then returned as a bounce back.

1. Check whether the email Is actually sending

The first thing to determine is whether the message is:

• Not sending at all

• Stuck in the outbox

• Sending and then bouncing back

If the email is not sending, the mail program or webmail will usually display an error message. That message is often the best clue to what is wrong, so it is important to read it carefully.

If the message is bouncing back, the returned email will normally include details about why delivery failed, such as the recipient address being invalid, the server rejecting the message, or the message being too large.

2. Make sure your SMTP server is configured correctly

If you are sending email through an email client such as Outlook, Apple Mail, or Thunderbird, one of the most common causes is an incorrect SMTP server configuration.

Things to confirm include:

• The outgoing mail server name is correct

• The port number is correct

• The correct encryption type is selected, such as SSL or TLS

• SMTP authentication is enabled if required

• The username is set to the full email address, if needed

• The password is correct and up to date

If your email is hosted with Rebel, you are able to check your email settings by going to our email setup assistant. 

3. Check the size of attachments

Large attachments are another common reason emails fail to send. Most email services and mail servers have limits on how large a message can be, including attachments.

If you are trying to send:

• large images

• video files

• multiple documents

• compressed folders

The message may be rejected for exceeding the allowed size.

If the file is too large, try:

• compressing the file

• reducing image sizes

• splitting attachments into separate emails

• uploading the file to cloud storage and sharing a link instead

4. Review the error message carefully

If the email is not sending, the error message often explains the problem. For example, it may indicate:

• authentication failed

• connection timed out

• relay access denied

• mailbox unavailable

• message size exceeded

• recipient address rejected

These errors can point to problems with login details, server settings, server availability, or the recipient’s email address.

If you are using webmail, it should usually display an error on screen when sending fails. That message can help identify whether the issue is with the message itself, the recipient, or the server. If you are still unsure, please contact our customer service team, and we can take a closer look.

5. Test sending from webmail

A helpful troubleshooting step is to try sending the same message through webmail.

This can help determine whether the issue is:

• with the email account itself

• with the email client

• with the local device or browser

If the message sends successfully through webmail but not through your email program, the issue is more likely related to the email client settings. 

If it also fails in webmail, the problem may be with the account, the message, or the mail server. Please contact our customer service team so we can take a closer look at this for you. 

6. Check browser extensions or plugins in webmail

If you are using webmail and the message will not send, a browser extension or plugin may be interfering with the page.

This is especially possible if you use:

• ad blockers

• privacy extensions

• script blocking tools

• security browser add-ons

Try opening Webmail in:

• a private or incognito window

• a different browser

• a browser with extensions temporarily disabled

If sending works afterward, a browser plugin may have been causing the issue.

If you are experiencing issues or have any questions, please feel free to contact our support team at service@rebel.com anytime, or you are able to speak to a live agent through chat or call 1-866-642-1232