My email won't send or receive messages: what to check in Duplika

When a mailbox reaches 100% of its space, it stops receiving messages and may stop sending them. Check the mailbox usage in cPanel and, if it is at the limit, increase the space from Email Accounts.

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

If you use POP3 and your client does not delete messages from the server, webmail will fill up over time. In that case, we recommend using IMAP, which keeps messages synchronized on the server. The differences and ports for each protocol are listed in POP3, IMAP, and SMTP: email differences and ports.

If the error mentions 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 the account settings.

The correct details for your email client are: incoming and outgoing server mail.tudominio.com (replacing tudominio.com with your site'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 does not 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 from cPanel and configure the client again. If the client repeatedly makes failed attempts with an incorrect username or password, the connection may become blocked: check the credentials and verify that you can access 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. In that case, ask your internet provider for a clean IP address.

The exact bounce text determines the solution:

• 550 5.7.1 [CS] Message blocked: our antispam system detected characteristics of unwanted email; this may be a false positive triggered by words, URLs, or uppercase subject lines in the message. The same bounce includes a link to report it, and once it has been reported, outgoing messages will work normally. If the problem recurs, forward the bounce to support so we can review the reason.

• 550 5.7.1 [ESA] Sender blocked: sending from your account has been blocked, frequently because it was used to send spam. Change the mailbox password from 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. Review your address list, remove addresses that do not exist, and send the message 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 recorded too many bounced or deferred emails. The two most common causes are:

• Your domain has SPF enabled without including our email service. Review the configuration in SPF and DKIM configuration.

• Someone gained access to your mailbox and is sending emails while impersonating you. Change the password as soon as possible and check who sent those emails using the Track Delivery tool.

Emails that WordPress sends with PHPmail are often filtered as spam by providers such as Gmail or Outlook. Configure the form sender to use an existing account on your domain: a nonexistent sender or one from another domain will cause sending to fail. For sending, use that account's SMTP: in WordPress, we recommend the FluentSMTP plugin. If only some application emails fail, check the plugin or the code that generates them. Step-by-step configuration is available in Improve WordPress email delivery using SMTP.

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

If port 25 is filtered by your internet provider, use port 9025 for unencrypted sending or port 465 for sending with SSL.

All hosting plans have an hourly email-sending limit for the entire account: Inicio 100, Esencial 200, Avanzado 300, Profesional 400, Empresa 500, Roble 600, and 200 per hour on reseller plans. Details are available in Email sending limits.

If you send 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 work again after renewal.

• Domain suspended for contact verification: if the bounce says You have reached a domain that is pending ICANN verification, the domain has been suspended until contact details are 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, with both set to DNS Only.

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

If expected emails arrive in spam, mark them as Not spam from webmail and add the sender as trusted under Settings > Preferences > Mail Account Settings > Antispam. We can also add the sender's domain to the allowlist under Spam Filters in cPanel.

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

We do not recommend disabling the antispam filter as the first measure: this allows genuine unwanted email through along with legitimate messages.

When the recipient is 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 does not pass the receiving server's SPF, DKIM, or DMARC verification.

Review and correct those records from cPanel, under Email Deliverability: on shared hosting, SPF must include spf.duplika.com. The complete configuration is available in SPF, DKIM, and DMARC configuration to validate your emails.

Having correct SPF, DKIM, and DMARC records prevents these bounces, but it does not guarantee that the message will reach the primary inbox: the recipient may still apply content rules that send it to spam.

A misconfigured forwarder disrupts receiving even when the original mailbox is configured correctly. In cPanel, under Forwarders, check that each forwarder points to an existing address: one pointing to a nonexistent address can cause messages sent to the original account to bounce.

If you find a forwarder that you did not configure, delete it and change the mailbox password as soon as possible. Forwarders to external accounts may also contribute to your outgoing messages being blocked by antispam.

Errors such as 550 5.1.1 Recipient address rejected are issued by the server receiving the email, not ours: the address does not exist or that server is blocking the message. In the bounce, check which server returns the error; if it is not 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 notice such as Warning: message delayed 24 hours is not a definitive bounce: the message remains queued and delivery attempts continue. If the destination server does not accept it after the retries, the message is returned with the reason. Contact us with the complete notice so we can follow up.

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

If you also manage DNS through Cloudflare or another provider, changes made in the cPanel zone do not modify the public records. How to check changes is explained in DNS propagation: how long it takes and how to check a change.