Emails - Blocking

In this article you will learn:

• Under what circumstances does email blocking occur
• How to deal with blocking:
  • sending emails
  • receiving emails
• Frequently Asked Questions

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Blocking emails

By blocking emails, we commonly mean a situation where a mail server refuses to send or receive an email for some reason. Another common problem is the setting of domain DNS records, which can appear to block emails on receipt.

Blocking of emails may occur:

• Before sending an email, for example, by blocking SMTP or the PHP mail() function on the web host. Address the problem with your email service provider.
• Before receiving an email, for example, routing failure or message rejection. The problem can be on both the recipient and sender side.

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Blocking sending

If you have blocked sending mail on your mailhost, webhost, WMS or WebSite, the system will not allow you to send any messages. The mail client will usually return an error message, scripts fail.

Common reasons for blocking emails include:

• Exceeding the daily quota, for example, when sending bulk mail or due to incorrect client settings
• Preventive blocking due to suspicious behaviour
• Full mailbox including trash and SPAM folder
• Another reason

Daily quota

You can send emails from web hosting services in two ways - using SMTP mail protocol or PHP mail() function. Each way has its own quota for sending emails (usually 500 emails per day, 50 for web hosting with LowCost tariff).

If you exceed your quota, the system will block you from sending mail in that way until midnight, when it resets the quota.

Preventive blocking

If we detect problematic behaviour in emails from our hosted mailbox or the entire service, we block it to prevent the spread of damage and negative spam ratings on our email servers. Similar to the daily quota, we distinguish between sending mail via SMTP and the PHP function mail().

Common causes of mail blocking by us include: 

• sending spam from an unsecured form or compromised mailbox
• violation of the conditions for sending emails

If we block your mail, the technician will send an email to the service subscriber with instructions on how to resolve the issue. Take the recommended action and then request removal of the block in response to the technician's message.

Full mailbox

If the mailbox is full, it continues to send emails but does not store them in Outbox or Concepts. 

You can solve the situation by increasing the capacity of mailboxes according to the Emails - Increase mailbox space instructions, or by deleting emails according to the WebMail - Delete emails instructions.

Other server upload blocking

If you suspect that the server is not sending emails even though the service is not restricted, please ask for a support check via the ⧉ form. Please specify:

• method of sending emails (SMTP via mail client or script, PHP mail)
• the most accurate date and time of sending the test message
• e-mail address of the sender
• e-mail address of the recipient
• the full text or a screenshot of any error message

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Blocking reception

If the message is blocked by the recipient's server, the sender will usually receive an undeliverable message describing the reason for the rejection. This message (or the fact that it doesn't arrive at all) is the easiest way to tell if the delivery failed due to server rejection or some other error.

Common reasons for blocking email reception include:

• Problems with SPF and DKIM, mechanisms that prevent spam
• Overflowing recipient mailbox
• Blacklisting the sender or its server
• Missing PHP mail() settings, specifically the return-path reply address

Problem with SPF and DKIM

Problems with SPF and DKIM can lead either to messages being dropped into spam (in which case the recipient's server does not send a non-delivery message), or to messages being rejected and the sender being notified.

An SPF is a DNS record of type TXT that lists the servers that are authorized to send e-mail from addresses in this domain. For more information and instructions on how to set up an SPF record, see the Email - SPF record article, or contact your email provider.

The error message for incorrect SPF setting varies by recipient, VEDOS sends an error:

550 5.7.1 <adresa@prijemce.tld>: Recipient address rejected: Please see http://www.openspf.net/Why?s=... (in reply to RCPT TO command)

To set up DKIM correctly, verify that you have the following records in DNS:

Name Type Data
key1.wedos-dkim._domainkey CNAME key1.dkim-we.wedos.net
key2.wedos-dkim._domainkey CNAME key2.dkim-we.wedos.net

For domains directed to Webhosting, WMS, or WebSite, the system generates these records automatically.

Overflowing mailbox

If the mailbox is full, it cannot receive any more emails. 

You can solve the situation by increasing the capacity of mailboxes according to the Emails - Increase mailbox space instructions, or by deleting emails according to the WebMail - Delete emails instructions.

Blacklisting

The server can reject a message based on a blacklist, where it finds either an e-mail address (a specific mailbox or an entire domain) or the IP address of the mail server.

There are a large number of blacklists. One of them can be configured directly by the user, for example according to the article Emails - Blacklist and whitelist customer administration. From the server where your address is blacklisted in this way, a message will be returned to you after a certain period of time:

550 5.7.1 <adresa@prijemce.tld>: Recipient address rejected: sender blacklisted

Other blacklists are public or internal, and you ask the sender's mailserver operator to remove the address from the blacklist. So if you send an email from our Webhosting, WMS, or WebSite, and you get an undeliverable message mentioning the location of the IP address of the mail server on the blacklist, send us the text of the error message via the form ⧉. A technician will take further action.

PHP mail() and return-path

If your emails sent via the PHP function mail() are not delivered, check that it contains the return-path parameter correctly filled in according to the pattern:

mail('adresa@prijemce.tld','Subject','Message Text','','-f adresa@odesilatele.tld');

Avoid setting the return-path to the address entered by the user in the form and instead use the address on the domain from which you are sending the email.

Other blocking of reception on the server

If you suspect that the server is not accepting emails even though the sender's domain has a correctly set minimum SPF record and there is enough free space in the mailbox, ask for a support check via the form. Please state:

• the most accurate date and time of sending the test message
• e-mail address of the sender
• e-mail address of the recipient
• the full text or a screenshot of any error message

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Frequently Asked Questions