This article deals with problems caused by mail servers blocking emails. If the blocking occurs on the side of the email client, with the exception of WebMail ⧉, resolve the problem using the manual or support of that client.
Other problems with email operation are covered in the article Email – Troubleshooting.
In this article you will learn:
- Under what circumstances emails are blocked
- How to resolve blocking of:
- Frequently Asked Questions
Email blocking
By email blocking we usually mean a situation where a mail server refuses, for some reason, to send or receive an email. Another common problem is the DNS record settings of a domain, which may look like email blocking on receipt.
Emails may be blocked:
- Before the email is sent, for example by blocking SMTP or the PHP mail() function on Webhosting. You resolve this problem with your email service provider.
- Before the email is received, for example by a routing failure or rejection of the message. The problem may be on the side of the recipient or the sender.
Blocked sending
If sending mail is blocked on your Mailhosting, Webhosting, WMS or WebSite, the system will not allow you to send any message. The email client will usually return an error message and scripts will fail.
Common reasons for blocked 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 the SPAM folder
- Other reason
Daily quota
The system resets the daily email quota automatically 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: using the SMTP mail protocol, or the PHP mail() function. Each method has its own quota for sending emails (usually 500 emails per day, 50 for Webhosting with the LowCost plan).
If you exceed the quota, the system blocks sending mail by that method until midnight, when the quota is reset.
Preventive blocking
If we detect problematic behavior in the emails of a mailbox or an entire service hosted by us, we block it to prevent the spread of damage and a negative spam rating of our email servers. As with the daily quota, we distinguish between sending mail via SMTP and via the PHP mail() function.
Common reasons why we block mail include:
- sending spam from an insecure form or a compromised mailbox
- violation of the terms for sending emails
If we block your mail, a technician will send the service customer an email with instructions on how to resolve the problem. Carry out the recommended measures and then ask for the block to be removed in your reply to the technician’s message.
Full mailbox
If the mailbox is full, it still sends emails but does not save them to Sent or Drafts.
You can resolve the situation by increasing the mailbox capacity according to the guide Email – Increasing Mailbox Space, or by deleting emails according to the guide WebMail – Deleting Emails.
Other blocking of sending on the server
If you suspect that the server is not sending emails even though the service is not restricted, ask Support to investigate using the form ⧉. Please include:
- the method of sending emails (SMTP via an email 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
Blocked receiving
If the message is blocked by the recipient’s server, the sender usually receives a non-delivery message describing the reason for rejection. From this message (or from the fact that you receive nothing at all) you can most easily tell whether delivery failed because of rejection by the server or because of another error.
Common reasons for blocked email receiving include:
- Problems with SPF and DKIM, that is, mechanisms that prevent spam from being sent
- The recipient’s mailbox is full
- The sender or their server is on a blacklist
- 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 landing in spam (in which case the recipient’s server does not send a non-delivery message), or to their rejection and notification of the sender.
SPF is a DNS record of type TXT containing a list of servers authorized to send emails from addresses on that domain. You can find more information and a guide to setting up an SPF record in the article Email – SPF Record, or from your email provider.
The error message for incorrect SPF settings differs depending on the recipient; VEDOS sends the 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)
For correct DKIM setup, 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 pointed 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 the situation by increasing the mailbox capacity according to the guide Email – Increasing Mailbox Space, or by deleting emails according to the guide WebMail – Deleting Emails.
Blacklisting
A server may reject a message based on a blacklist, in which it finds either the 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 Email – Blacklist and Whitelist in the Customer Administration. After some time, the server on which your address is blacklisted in this way will return the message:
550 5.7.1 <adresa@prijemce.tld>: Recipient address rejected: sender blacklisted
Other blacklists are public or internal, and you request removal of an address from a blacklist from the operator of the sender’s mail servers. So if you send an email from our Webhosting, WMS or WebSite and receive a non-delivery message mentioning that the mail server’s IP address is on a blacklist, send us the text of the error message using 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 it contains a correctly filled-in return-path parameter following this pattern:
mail('adresa@prijemce.tld','Předmět','Text zprávy','','-f adresa@odesilatele.tld');
Avoid setting the return-path to an address entered by the user in a form; use an address on the domain from which you send the email instead.
Other blocking of receiving 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 set up correctly and there is enough free space in the mailbox, ask Support to investigate using 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 a day. How can I arrange that?
If you need to send newsletters and other bulk correspondence, even if solicited, which our termsprohibit, use a bulk email sending service. If 500 emails a day are not enough for your regular correspondence, contact us using the form ⧉. Please include the name of the hosting service, your proposed new daily limit and the reason for your request.
What is the daily limit for anyway? Can you reset it?
The daily limit serves to restrict the overall mail sent by our servers, because the volume of emails sent determines how spam filters treat the mail coming from them. The system resets the limit every day at midnight; customer support does not intervene in this process.
Proč mojí poštu neustále blokují na základě IP adresy? Nemůžete to nějak koncepčně vyřešit?
Zjednodušeně řečeno – sdílený Webhosting provozuje na jednom web serveru velké množství webových stránek, a na jenom mailovém serveru velké množství e-mailových schránek.
If someone attacks a website on the same server as your site, the attack affects you even though it is not aimed directly at you. It is the same with email. If a large amount of mail, especially spam, is sent from one server because another user has a compromised mailbox, blacklisting affects you too, even though you are not causing the problems. This is the biggest problem of shared services, and it simply cannot be eliminated completely. An alternative is to run your own mail server, where you have everything to yourself and fully under your control, but the cost (hardware, software, administration, …) is in a completely different league.
Why do emails arrive in WebMail but not in the email client?
The email client may be configured incorrectly for receiving mail, sending, or both. Common errors are resolved by the correct configuration of servers, ports and security according to this guide. If the problems persist, resolve the error with the support of the email client.