Emails Bouncing Back? How to Fix Bounce Errors

Emails Bouncing Back? How to Fix Bounce Errors

If emails you send come back with a bounce message, the fix depends on the error code in that message. This guide explains how to read a bounce-back, the most common causes, and how to fix the ones you can control from your hosting account.

How to Read a Bounce-Back Message

Every bounce message includes an SMTP reply code and, usually, an enhanced status code written as three numbers separated by dots (for example 5.1.1). The enhanced code is more useful than the three-digit code alone, because it tells you specifically whether the problem is an invalid address, a policy rejection or a blacklist block.

Bounce codes fall into two families:

• 5xx — permanent failure ("hard bounce"). The server will not deliver the message and will not try again.
• 4xx — temporary failure ("soft bounce"). The server will usually retry automatically for a period before giving up.

Greylisting: some mail servers deliberately reject the first delivery attempt from a sender they don't recognise, expecting a legitimate server to try again shortly after. This shows up as a 450/451 temporary bounce and normally clears itself within minutes.

Causes on the Recipient's Side

Some bounces happen because of a problem at the recipient's end, not yours. These cannot be fixed from your hosting account:

• A typo in the address, or the mailbox has been deleted (550/551)
• The recipient's mailbox is full (552) — this keeps failing until they clear space
• The message or attachment is too large for their mail server — many providers reject anything over roughly 25MB (Gmail) or 10MB (Outlook)

If you see one of these, contact the recipient another way or resend a smaller message later.

Causes You Can Fix on Your Hosting Account

Fix 1: Add or Repair SPF, DKIM and DMARC Records

This is the most common fixable cause of bounces and spam-folder delivery. Gmail and Yahoo require incoming mail to be authenticated: without valid SPF and DKIM records, mail from your domain can be rejected outright, and a domain with no DMARC record is treated with more suspicion.

In cPanel:

1. Log in to cPanel and go to Email → Email Deliverability.
2. Check the status shown for SPF, DKIM and DMARC on your domain. A green check means it is passing; a red warning or "Invalid" status needs action.
3. If it shows "PROBLEMS EXIST", click Repair. cPanel will generate the correct records and update your DNS zone automatically.

If your domain's DNS is managed elsewhere (for example, at your registrar or through Cloudflare), the Repair button cannot update those external records. Instead, click Manage next to the domain in Email Deliverability, note the DKIM and SPF values shown, and add them manually in your external DNS provider's control panel.

In DirectAdmin: go to Email Accounts → Enable DKIM for the domain. If the domain's DNS is hosted externally, copy the DKIM TXT record across to that external DNS too — otherwise outgoing mail will be signed with DKIM but the signature checks will fail, which is worse than having no DKIM at all.

DMARC caution: avoid setting a strict policy (p=reject combined with strict alignment) too early. This can cause recipients to drop legitimate mail with a 550 "spam classified" bounce. If you see this, relax alignment or set the policy to p=quarantine while you investigate.

Fix 2: Check Forwarded Mail

If you forward mail from one address to another and the forwarded copy bounces, SPF can be the cause: forwarding can break the SPF check on the resent message. This is a server-side setting, so if you suspect this is happening, open a support ticket and we can check it.

Fix 3: Check Your Outgoing Server Settings

Wrong SMTP settings in your email client can also cause messages to fail to send, which can appear as a bounce. Verify these in your email client:

The most common mistakes are using port 25 (blocked by most internet providers), using STARTTLS instead of SSL/TLS, or leaving authentication disabled. Your email client must authenticate with the outgoing server using your email address and password, or the server will refuse to send.

In Outlook: go to File → Account Settings → select your account → Change → More Settings → Outgoing Server → tick "My outgoing server requires authentication".

On iPhone/iPad: go to Settings → Mail → Accounts → your account → SMTP → tap your server → set Authentication to Password.

On Android: open your email app's account settings → Outgoing server → make sure "Require sign-in" is enabled.

Fix 4: Check Your Password

Your email sending password is the email account password set in cPanel or DirectAdmin — not your Hostking client area password. Verify it by logging into webmail at mail.yourdomain.com. If you can log in there, the password is correct; if not, reset it under Email Accounts in your control panel.

Fix 5: Check Your Sending Limit

Hosting plans apply an hourly email sending limit to prevent abuse and keep your domain's reputation clean. If you reach the limit, further outgoing mail is temporarily held or blocked until the limit resets, which can look like a bounce. For your plan's current limit, check the Email section of your control panel or your welcome email.

If you need to send bulk email or newsletters, use a dedicated email sending service such as Mailchimp, SendGrid or Brevo rather than your hosting email account.

Fix 6: Check if Your Domain is on a Blacklist

If your emails have previously been flagged as spam, your domain or IP may have been added to a blacklist, which produces a 550 or 554 bounce. Check at mxtoolbox.com/blacklists. If your domain appears on a blacklist, open a support ticket and we'll help you get it removed.

Still Getting Bounces?

Open a support ticket from the client area at my.hostking.host, or use live chat on the website, and include:

• The email address you sent from
• The full bounce-back message, including the SMTP code
• The email client and device you're using
• A screenshot if possible

Live chat is available 7 days a week, and support tickets are answered from the client area.