Currently, sometimes it is not easy to deliver emails into the target mailboxes, because all mailservers want to protect the owners of mailboxes against spams, phishing, fraudulent messages ... No system is able to distinguish spams and legit emails a hunderd per cent, also because some emails are considered as spam by some people but as legit by other people.
If the
mailserver of the recipient rejects your email, the smtp server generates
non delivery message and sends it to the
Envelope Sender address (if the email was sent from web, the Envelope Sender is
postmaster@web-domain.tld)
The freuquent errors
The mailbox of the recipient does not exist or is unavailable from some reason. Here are some samples of corresponding errors
Sorry, no such mailbox here
Sorry, no user here by that name
Sorry, no mailbox here by that name
The email account that you tried to reach does not exist.
Recipient address rejected:
User unknown in relay recipient table
Recipient address rejected: User unknown in virtual alias table
Recipient address rejected: Access denied.
Recipient address rejected: undeliverable address:
Recipient address lookup failed recipient address rejected: Inactive
No such recipient here
Address rejected.
Mailbox unavailable.
Mailbox not available
Requested mail action aborted, mailbox not found
Requested action not taken: mailbox unavailable
Relay access denied
We don't relay mails
User unknown
The recipient mailbox is full
Sorry, recipient mailbox is full
The message size exceeds the limit set by the target mailserver
Sorry, that message size exceeds my databytes limit
Gmail has detected that this message is not RFC 5322 Messages missing a valid Message-ID header are not accepted.
The DKIM and SPF check of the domain of From header was not successful, see bellow
Your email has been blocked because the sender is unauthenticated. Gmail requires all senders to authenticate with either SPF or DKIM.
Your access to this mail system has been rejected due to poor reputation of a domain used in message transfer
Email was rejected as spam (it is recommend to contact the administrator of the target mailserver to get more details, why the email was evaluated as spam, or to ask the recipient to add your email address into the whitelist)
Spam message rejected. Message denied by policy
If you don't get the Non Delivery Message, it means that the target mailserver accepted your message. However, the recipient may not receive the message into their inbox. Or the message can be delivered into the Spam folder etc.
What the sender can do to improve delivering of their emails
Most mailservers require, that the domain in the From header is authenticated with either
SPF or
DKIM. And it is better, if this domain has also set the
DMARC record. So, at first you have to check, whether DKIM, SPF and DMARC records are set for your domain.
DKIM makes possible to verify, that the message comes from a mailserver authenticated to send emails from the domain. DKIM - DomainKeys Identified Mail is a technology of verifiing the origin of the email with asymmetrical decryption.
The SPF record determines which IPs are allowed to send the emails with the domain of the sender (the Envelope Sender is checked)
The DMARC check combines DKIM and SPF. Successful DMARC check means that the email has valid DKIM sign of the domain of the sender in the From header, or this domain is the same of the domain of the Envelope Sender and the SPF check passes (at least on of DKIM and SPF check has to be successful)DKIM
We activate automaticaly DKIM for new hostings, which use DNS servers of Forpsi. You can check the status of DKIM or activate it, se the article
DKIM.
DKIM is activated only for emails sent via smtp server smtp.forpsi.com (also from webmail).
If you send emails from a web with the PHP mail() function or via other smtp servers (smtp server of the ISP ...) and
your emails are not delivered, we recommend to try to send the emails via smtp server smtp.forpsi.com. Redact systems allow to set sending emails via an entered smtp server, it is neccessary to fill in authentication. You can use PHP Mailer instead of the PHP mail() function. The
domains of the From header and of the Envelope Sender have to be the same to sign the email with a valid DKIM sign.
SPF
We set
automaticaly the SPF record with the Fail (-all) policy for new hostings, which use DNS servers of Forpsi. The Fail policy was chosen to prevent abusing of domains in fraudulent messages.
You can check the SPF record or set it, see the article
Setting of SPF and DMARC records. Every domain can have only one SPF record. If you want to allow more mailservers in the SPF record, all items have to be included in one SPF record.
DMARC
We set automaticaly the DMARC record with the qurantine policy for new hostings, which use DNS servers of Forpsi. The quarantine policy was chosen because some mailservers require the DMARC with at least quarantine policy. If you want to protect your domain against abusing in fraudulent emails, change the policy to reject.
When DKIM, SPF and DMARC don't help
After setting of the DKIM, SPF and DMARC records, it is neccessary to wait at least 30 minutes till the changes are reflected on all cache DNS servers.
If you get a None Delivery Report (in case of emails sent from webs into the mailbox postmaster@), follow the text of the error in the NDR message.
If you don't get the NDR message till 24 hours after sending either, it means, that the target mailserver accepted the message. Then we recommend to contact the support of this target mailserver, which didn't deliver your email into the target mailbox, although it accepted it. The reason, why the email wasn't delivered, can be bad reputation of your domain (if it appeared in emails reported by their recipients as spam), or oposite your domain is new and it hasn't established any reputation, and other and other.
In the article
Email has returned back with error "Your access to this mail system has been rejected due to poor reputation of a domain used in message transfer", we describe the situation for Centrum.cz (Atlas.cz, Volny.cz) or banks (Allianz, ČSOB, KB, Kooperativa, UniCredit,...), that use the antispam system of the company Cisco Talos Sender Domain Reputation (SDR). Centrum.cz write in their knowledge base: "If, even after checking the correct message settings, your emails still do not pass through our servers, contact us at the email address
helpdesk@economia.cz."
In case of other mailserver, it is similar. If the mailservers accept the message and don't deliver it into the target mailbox, or deliver it into the Spam folder, it is neccessary to contact the support of the target mailserver to provide more information about evaluating your email as spam.