My email isn't sending or receiving messages: what to check in Duplika

When a mailbox reaches 100% of its storage, it stops receiving messages and may also stop sending them. Check the mailbox usage in cPanel and, if it's at its limit, increase its storage under Email Accounts.

Also check your plan's total storage in cPanel, under Disk Usage: if your hosting account has run out of space, email will stop coming in and going out even if each mailbox still has available storage.

If you use POP3 and your email client doesn't delete messages from the server, Webmail will fill up over time. In that case, it's best to use IMAP, which keeps messages synchronized on the server. Learn about the differences and ports for each protocol in POP3, IMAP, and SMTP: email protocol differences and ports.

If the error says Plaintext authentication disallowed on non-secure (SSL/TLS) connections, your client is trying to connect without encryption. For security reasons, we only allow SSL or TLS connections: enable SSL/TLS in your account settings.

The correct settings for your email client are: incoming and outgoing server mail.tudominio.com (replace tudominio.com with your website's actual domain), your full email address as the username, IMAP on port 993, POP3 on port 995, and SMTP on port 465, all with SSL enabled. If your client won't connect on port 465, try port 587 with TLS.

If the error is SMTP Error: Could not authenticate, the login details are incorrect: reset the mailbox password in cPanel and set up the client again. If the client repeatedly tries to connect with an incorrect username or password, the connection may be blocked: check your credentials and make sure you can sign in to Webmail with the same account.

If connection errors affect POP, IMAP, and SMTP at the same time, your internet connection's IP address may be on a blacklist. If so, ask your internet service provider for a clean IP address.

The exact text of the bounce determines the solution:

• 550 5.7.1 [CS] Message blocked: our antispam system detected characteristics of spam; this may be a false positive triggered by words, URLs, or an all-caps subject line in the message. The bounce includes a link to report it. Once reported, messages will send normally. If the problem happens again, forward the bounce to Support so we can investigate the reason.

• 550 5.7.1 [ESA] Sender blocked: sending from your account has been blocked, often because it was used to send spam. Change the mailbox password under Email Accounts in cPanel, check your computers for viruses or malware, and let us know so we can restore sending.

• 550 5.7.1 [IRR] Our system has detected unusual activity from your account: many messages were sent to invalid recipients. Check your address list, remove addresses that don't exist, and send the messages again.

• 550 This message was classified as SPAM and may not be delivered: this is usually an antispam false positive. Forward the bounce to Support so we can review it.

The server rejects your outgoing messages for at least 60 minutes because it has recorded too many bounced or deferred emails. The two most common causes are:

• Your domain has SPF enabled but doesn't include our email service. Check the settings in SPF and DKIM settings.

• Someone accessed your mailbox and is sending emails pretending to be you. Change the password as soon as possible and use the Track Delivery tool to check who sent those emails.

Emails sent by WordPress using PHPmail are often filtered as spam by providers such as Gmail or Outlook. Set the form's sender address to an existing account on your domain: using a nonexistent address or one from another domain will cause sending to fail. Use that account's SMTP server to send messages; for WordPress, we recommend the FluentSMTP plugin. If only some application emails fail, check the plugin or code that generates them. Follow the step-by-step instructions in Improve email sending from WordPress using SMTP.

If your application sends through an external SMTP server (for example, Amazon SES or another provider), contact us: we enable access to external SMTP services on our end.

If your internet service provider filters port 25, use port 9025 to send without encryption or port 465 to send with SSL.

All hosting plans have an hourly limit on the number of emails sent across the entire account: Starter 100, Essential 200, Advanced 300, Professional 400, Business 500, Roble 600, and 200 per hour on reseller plans. See Email sending limits for details.

If you're sending from an application that opens many connections at the same time, keep the number of connections below 100 every 30 seconds.

If you need to send a higher volume, consider a Cloud Servers plan with a dedicated IP or an email marketing plan.

When no messages are coming in or going out, check the following in order:

• Expired domain: if the sender's domain has expired, outgoing messages bounce with 550 5.1.2 [SDNF] Sender Domain Not Found. Renew the domain; email may take a few hours to start working again after renewal.

• Domain suspended due to contact verification: if the bounce says You have reached a domain that is pending ICANN verification, the domain has been suspended until the contact information is verified. Complete the verification to reactivate the domain.

• If you manage your DNS through Cloudflare, the A record for mail.tudominio.com must point to your server's IP address and the MX record to mail.tudominio.com; both must be set to DNS Only.

• Some recipients return 451 4.7.650 The mail server has been temporarily rate limited due to IP reputation. This is a temporary block managed by the recipient's provider; if you receive this bounce, contact us so we can follow up.

If the emails you were expecting go to spam, mark them as Not spam in Webmail and add the sender as a trusted contact under Settings > Preferences > Mail Account Configuration > Antispam. We can also add the sender's domain to the allowlist under Spam Filters in cPanel.

If messages don't even appear in the spam folder, the filter may be deleting them automatically: under Spam Filters in cPanel, Automatically Delete New Spam (Auto-Delete) deletes email identified as spam. Disable this option or add the sender to the allowlist under Show Additional Configurations to keep those messages.

We don't recommend disabling the antispam filter as a first step: that lets real spam through along with legitimate email.

When the recipient is using Gmail, the bounce says 550-5.7.26 Your email has been blocked because the sender is unauthenticated and asks you to authenticate the domain with SPF or DKIM. In Microsoft and Outlook, the message is 550 5.7.515 Access denied, sending domain doesn't meet the required authentication level. Both indicate that your domain failed the receiving server's SPF, DKIM, or DMARC check.

Check and correct these records in cPanel under Email Deliverability: on shared hosting, the SPF record must include spf.duplika.com. See SPF, DKIM, and DMARC settings to authenticate your emails for the complete setup.

Correct SPF, DKIM, and DMARC records prevent these bounces, but don't guarantee that the message will reach the inbox: the recipient may still apply content rules that send it to spam.

A misconfigured forwarder can disrupt email delivery even when the original mailbox is set up correctly. In cPanel, under Forwarders, check that each forwarder points to an existing address: a forwarder that points to a nonexistent address may cause messages sent to the original account to bounce.

If you find a forwarder you didn't set up, delete it and change the mailbox password as soon as possible. Forwarders to external accounts can also contribute to antispam systems blocking your outgoing messages.

Errors such as 550 5.1.1 Recipient address rejected are issued by the server receiving the email, not ours: the address doesn't exist or that server is blocking the message. Check the bounce to see which server returned the error. If it isn't a Duplika server, the solution depends on the recipient: verify that the address is spelled correctly, and if it is, ask their administrator to check why your messages are being rejected.

A notification such as Warning: message delayed 24 hours isn't a final bounce: the message is still queued and delivery attempts are ongoing. If the destination server doesn't accept it after the retries, the message will be returned with the reason. Contact us with the complete notification so we can follow up.

If your domain uses the MX records for Google Workspace, Microsoft 365, or another provider, that provider—not Duplika's email servers—handles incoming messages. Forms and applications hosted with us may still try to deliver messages locally: in cPanel, Email Routing determines whether the server delivers messages locally or remotely; adjust it based on where the mailbox is hosted.

If you also manage DNS through Cloudflare or another provider, changes you make in the cPanel zone won't update the public records. Learn how to check for changes in DNS propagation: how long it takes and how to check a change.