Email errors can be frustrating, especially if they are cryptic, like “554 no smtpd here“.

You know that the recipient rejected the message, but why?

Here at Bobcares, we often help website owners to resolve such email errors as part of our Outsourced Technical Support services for web hosts.

Today, we’ll see the top 3 reasons for the error “554 no smtpd here”  and how we fix it.

What is “554 no smtpd here” error?

In a normal mail delivery, mail goes from the sender, to the sending MX, and to the recipient’s MX, and then to the recipient.

How email works?

Sometimes, not all emails reach the destination server. The recipient server performs a series of checks to prevent fraud emails.

If the recipient server has doubts about the sender’s authenticity, it rejects such emails with a bounce message.

For instance, a sample bounce message looks like this:

51-4.0 554-NO SMTP service 451-4.0 554 bad DNS PTR resource record

There are many variants of this error message:

554 No SMTP service here
554 No smtpd here554: host refused to talk to me

Although, the error messages differ, the reasons for the error are common.

“554 no smtpd here” error – Causes and Fixes!

Now, let’s have a look at the various reasons for the error “554 no smtpd here” and how our Support Engineers fix them.

1) Poor IP reputation

In our experience handling email issues, the common reason for this error is bad reputation of the sender’s IP address.

In other words, the bad reputation of the IP address from which the mail originates from.

The reputation of the IP can go bad when there is repeated spamming instances, open relays or unacceptable behavior of the mail server.

Eventually, the mail server IP will be blacklisted in spam monitoring systems like SORBS, DNSBL, Barracuda, etc.

How we fix?

Here, our Support Engineers ensure that the sending IP is clean. Online tools like https://mxtoolbox.com/blacklists.aspx comes handy here.

If the IP is blacklisted, we identify the source of the spam or security vulnerability, resolve it and take the corrective/preventive actions on the server. After that, we submit a delist request.

Usually, delist will take around 2 to 3 days.

2) Bad DNS records

Similarly, the recipient server rejects the emails due to the issues in the DNS records of the sender domain.

That is, recipient server checks the DNS records like SPF, DKIM, PTR to check whether the sender is a genuine one. If any mismatch noted, it will reject the emails.

Let’s take a look at these 3 records in detail.

i) SPF record

Email providers use a security feature called SPF(Sender Policy Framework) to verify the sender’s authenticity. It decides the servers that can send emails on behalf of a domain.

That is, the SPF record contains the IP addresses of servers that can send emails on behalf of the domain. If the email is from an IP listed in SPF entry, the recipient server accepts mail.

We’ve seen cases where mail server IP has changed, but the SPF record doesn’t contain this new IP address. For the recipient server, the mail originates from the IP address that is not added in the SPF record.

Result is “554 no smtpd here” error.

ii) PTR record(Reverse DNS)

Reverse DNS(PTR records) map IP address to domain names and help to validate a server.

That is, if a server “abc.mailserver.com” points to IP 192.xx.xx.35, the reverse DNS of the IP should be “abc.mailserver.com”.

The vast majority of spam mails are sent from an infected PC or a poorly maintained mail server.

These servers usually have a sloppy hostname and an IP without a PTR record.

Large email providers, like Hotmail, use this as an important indicator of the source of spam and reject emails from such senders.

iii) DKIM records

DKIM is a method to prevent email spoofing.

It associates the domain name with an email message by attaching a digital signature. As a result, the recipient server can identify if emails are from the valid domain.

If there are no DKIM records, some mail servers assume that the sender is fake and reject the email.

How we fix?

Our Support Engineers verify the SPF, PTR and DKIM records of the domain. When there is a mismatch, we correct it by making required changes in these records.

For PTR records, we always choose a name that is different from the default entry of the provider, like “xxx-xxx-xxx-xxx-static.provider.tld“. It’s always advisable to use a fully qualified domain name(FQDN).

For example, “abc.mailserver.com”.

For the servers we manage, we always configure critical email records like SPF, PTR, DKIM, etc. to ensure reliable email deliveries.

3) Recipient errors

Similarly, the mail delivery error “554 no smtpd here” may also be caused by issues on the recipient’s mail server.

This includes incorrect MX entry for the recipient domain, suspended or disabled recipient email account, custom blacklists or filters configured on the recipient side, etc.

How we fix?

We verify that MX records are set correctly for the recipient domain using the command:

dig domain.com MX

Further, we check the connection to the recipient mail server with the following command.

telnet domain.com 25

If we notice missing MX entries or connection problems on the receiver side, then this must be fixed at the receiver side.

In case of custom blacklists or filters, the sender domain needs to be whitelisted at the recipient end to allow mail flow.

Conclusion

To sum up, email error “554 no smtpd here” can happen mainly due to wrong DNS settings of the domain, IP blacklists, etc. Today, we’ve discussed the top 3 causes for this error and how our Support Engineers fix them.