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How to Fix "Cannot Send Mail" Error on iPhone / Apple Mail

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If you can receive emails on your iPhone or iPad but get a "Cannot Send Mail" error, a bounce-back, or a message stating that an email address was rejected when sending, the issue is almost always related to your Outgoing Mail Server (SMTP) settings in Apple Mail.
 
A common cause on iOS devices is that Apple Mail labels the SMTP Username and Password fields as (Optional) during setup. However, on our mail servers, SMTP authentication is strictly required.
 

How to Fix SMTP Settings in Apple Mail

  1. Open Settings on your iPhone or iPad.
  2. Navigate to Apps > Mail (or Mail > Accounts on older iOS versions).
  3. Tap your email account.
  4. Tap Account Settings and then select SMTP under the Outgoing Mail Server section.
  5. Tap your Primary Server.
  6. Ensure the following fields are filled out completely:
    • User Name: Enter your full email address (e.g., name@yourdomain.com). Do not leave this blank even if iOS says optional.
       
    • Password: Enter your email password. Do not leave this blank.
       
    • Use SSL: Toggle ON.
       
    • Authentication: Select Password.
  7. Confirm your Server Port and Encryption match your specific email setup (see server details below).
     
  8. Tap Done in the top-right corner to save your settings.

How to Verify Your Server Settings

We strongly recommend using IMAP for all mobile devices so your messages, folders, and sent items stay synchronized seamlessly across all your phones, tablets, and computers.
 

Option 1: Rebel Cloud Email Settings

(Note: Always use .com for Cloud Mail server addresses—do not use .ca).
  • For IMAP Accounts (Recommended):
    • Incoming Server: imap.rebel.com | Port: 993 | Encryption: SSL/TLS
    • Outgoing Server (SMTP): smtp.rebel.com | Port: 587 | Encryption: STARTTLS
    • Username: Full email address
    • Password: Email password
  • For POP3 Accounts:
    • Incoming Server: pop.rebel.com | Port: 995 | Encryption: SSL/TLS
    • Outgoing Server (SMTP): smtp.rebel.com | Port: 587 | Encryption: STARTTLS
    • Username: Full email address
    • Password: Email password

Option 2: Plesk Hosted Email Settings

(Replace yourdomain.com with your actual registered domain name).
  • For IMAP Accounts (Recommended):
    • Incoming Server: mail.yourdomain.com | Port: 993 | Encryption: SSL/TLS
    • Outgoing Server (SMTP): mail.yourdomain.com | Port: 465 | Encryption: SSL/TLS
    • Username: Full email address
    • Password: Email password
  • For POP3 Accounts:
    • Incoming Server: mail.yourdomain.com | Port: 995 | Encryption: SSL/TLS
    • Outgoing Server (SMTP): mail.yourdomain.com | Port: 465 | Encryption: SSL/TLS
    • Username: Full email address
    • Password: Email password

How to Troubleshoot Connection Issues

  • How to test for local Wi-Fi network blocks: Temporarily turn off Wi-Fi on your device and attempt to send an email using mobile data (LTE/5G). If it sends successfully over mobile data, your local Wi-Fi router or ISP may be blocking the outgoing SMTP port.
     
  • How to rule out server issues: Log in to Webmail via your web browser. If sending works normally from Webmail, your account and server are functioning properly, confirming the issue is isolated to the mobile app configuration.

How to Contact Support

If you have verified your settings and are still unable to send mail, our technical support team is available to help:

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