This article addresses problems with email blocking by mail servers. If blocking occurs on the email client side, except for WebMail ⧉, resolve the problem using the manual or support for the given client.
Other email operation problems are addressed in the article Emails – Troubleshooting.
In this article you will learn:
- Under what circumstances email blocking occurs
- How to resolve blocking:
- Frequently asked questions
Email blocking
By email blocking we usually mean a situation where a mail server refuses to send or receive an email for some reason. Another common problem is the configuration of a domain's DNS records, which may appear as email blocking upon receipt.
Email blocking can occur:
- Before sending an email, for example by blocking SMTP or the PHP mail() function on the webhosting. You resolve the problem with your email service provider.
- Before receiving an email, for example due to routing failure or message rejection. The problem may be on the recipient's or sender's side.
Sending blocking
If sending mail is blocked on your mailhosting, webhosting, WMS or WebSite, the system will not allow you to send any message. The mail client usually returns an error message, scripts fail.
Common reasons for blocking email sending include:
- Exceeding the daily quota, for example when sending bulk mail or due to incorrect client settings
- Preventive blocking due to suspicious behavior
- Full mailbox including the trash and SPAM folder
- Other reason
Daily quota
The system automatically resets the daily email quota every day at midnight (Central European Time). We do not perform manual resets on request.
From webhosting services you can send emails in two ways – via the SMTP mail protocol or the PHP mail() function. Each method has its own email sending quota (usually 500 emails per day, 50 for webhosting with the LowCost plan).
If you exceed the quota, the system will block sending mail by that method until midnight, when the quota is reset.
Preventive blocking
If we detect problematic behavior with email mailboxes or entire services hosted by us, we block it to prevent damage and negative spam scoring of our email servers from spreading. As with the daily quota, we distinguish between sending mail via SMTP and the PHP mail() function.
Common causes of mail blocking on our side include:
- sending spam from an unsecured form or a compromised mailbox
- violation of the terms for sending emails
If we block your mail, a technician will send the service subscriber an email with instructions on how to resolve the problem. Take the recommended steps and then reply to the technician's message requesting removal of the block.
Full mailbox
If the mailbox is full, it can still send emails, but it does not save them to Sent Mail or Drafts.
You can resolve this by increasing mailbox capacity according to the guide Emails – Increasing mailbox space, or by deleting emails according to the guide WebMail – Deleting emails.
Other sending blocking on the server
If you suspect that the server is not sending emails even though the service is not restricted, ask support to investigate via the form ⧉. Please include:
- the sending method used for emails (SMTP via mail client or script, PHP mail)
- the most precise possible date and time the test message was sent
- the sender's email address
- the recipient's email address
- the full text or a screenshot of any error message
Receiving blocking
If the recipient's server blocks the message, the sender usually receives a non-delivery message describing the reason for rejection. Based on this message (or on the fact that you do not receive any message at all), you can most easily determine whether delivery failed due to rejection by the server or another error.
Common reasons for blocking email receipt include:
- Problems with SPF and DKIM, that is, mechanisms preventing spam sending
- Recipient's mailbox is full
- Sender or their server being placed on a blacklist
- Missing PHP mail() settings, specifically the return-path reply address
Problem with SPF and DKIM
Problems with SPF and DKIM can either cause messages to end up in spam (in which case the recipient's server does not send a non-delivery message), or cause them to be rejected and the sender informed.
SPF is a TXT-type DNS record containing a list of servers authorized to send emails from addresses on this domain. More information and instructions for setting up an SPF record can be found in the article Emails – SPF record, or from your email provider.
The error message for incorrect SPF settings varies by recipient; VEDOS sends the following 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 configure DKIM correctly, verify that you have these 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.
Full mailbox
If the mailbox is full, it cannot receive any more emails.
You can resolve this by increasing mailbox capacity according to the guide Emails – Increasing mailbox space, or by deleting emails according to the guide WebMail – Deleting emails.
Blacklisting
The server may reject a message based on a blacklist, where it finds either an email address (a specific mailbox or an entire domain), or the IP address of the mail server.
There are many blacklists. One of them can be configured directly by the user, for example according to the article Emails – Blacklist and whitelist in the customer administration. From the server on which your address is blacklisted in this way, the message will return after some time:
550 5.7.1 <adresa@prijemce.tld>: Recipient address rejected: sender blacklisted
Other blacklists are public or internal, and you request removal of the address from the blacklist from the sender's mailserver operator. So if you are sending an email from our Webhosting, WMS, or WebSite, and you receive a non-delivery message mentioning the mail server IP address being placed on a blacklist, send us the text of the error message via the form ⧉. A technician will handle the next steps.
PHP mail() and return-path
If your emails sent via the PHP mail() function are not being delivered, check that the return-path parameter is filled in correctly according to the example:
mail('adresa@prijemce.tld','Subject','Message text','','-f adresa@odesilatele.tld');
Avoid setting return-path to an address entered by the user in the form; instead use an address on the domain from which you are sending the email.
Other receiving blocking on the server
If you suspect that the server is not receiving emails even though the sender's domain has at least an SPF record correctly set and there is enough free space in the mailbox, ask support to investigate via the form. Please include:
- the most precise possible date and time the test message was sent
- the sender's email address
- the recipient's email address
- the full text or a screenshot of any error message
Frequently asked questions
I need to send more than 500 emails per day. How can I arrange that?
If you need to send newsletters and other bulk, even solicited, correspondence that our terms prohibit, use a bulk email sending service. If 500 emails per day is not enough for ordinary correspondence, contact us via the form ⧉. Please include the name of the hosting service, your proposed new daily limit, and the reason for the request.
What is the daily limit for anyway? Can you reset it?
The daily limit serves to globally limit mail sent by our servers, because the amount of sent emails affects how spam filters behave toward mail originating from them. The system resets the limit every day at midnight; customer support does not intervene in this process.
Why is my mail constantly being blocked based on the IP address? Can't you solve this in some systemic way?
Simply put – shared Webhosting runs a large number of websites on one web server, and a large number of email mailboxes on one mail server.
If someone attacks a website on the same server where your sites are located, the attack affects you even though you are not being attacked directly. The same applies to mail. If a large amount of mail leaves one server, especially spam, because another user has a compromised mailbox, blacklisting will also affect you even though you are not causing the problems. This is the biggest issue with shared services, which simply cannot be completely eliminated. The alternative is operating your own mail server, where everything is yours and fully under your control, but the cost (hardware, software, administration, ...) is somewhere entirely different.
Why do emails reach WebMail but not the mail client?
The mail client may be incorrectly configured for receiving mail, sending mail, or both. Common errors can be fixed by proper configuration of servers, ports, and security according to this guide. If the problems persist, resolve the issue with the email client support.