Plesk customer email issue

AlpineHost · Sep 12, 2024

Hi all,

I have a customer in the US that is receiving a "host relay3.domain.com[IP Address] refused to talk to me: 554 relay3.domain.com" error on emails sent to his US Government email address and a few other domains, from our Plesk server. We have done an IP check on our side and we are all good, no blacklisting anywhere. SPF, DMARC and DKIM records are all confirmed to be correct. What will be the next step to check? Or, is this something that the customer needs to figure out on his own?

Thank you guys in advance for the feedback.

NizhalHosting · Sep 16, 2024

yes, ask the client to check his/her ip weather it is blacklisted , these things nowadays happens a lot, as all servers are protected by WAF firewall and securing their servers

AlbaHost · Sep 16, 2024

AlpineHost said:
Hi all,

I have a customer in the US that is receiving a "host relay3.domain.com[IP Address] refused to talk to me: 554 relay3.domain.com" error on emails sent to his US Government email address and a few other domains, from our Plesk server. We have done an IP check on our side and we are all good, no blacklisting anywhere. SPF, DMARC and DKIM records are all confirmed to be correct. What will be the next step to check? Or, is this something that the customer needs to figure out on his own?

Thank you guys in advance for the feedback.

Until you provide the complete failure email logs, we can just spekulate. Hide the details in the failed returning logs and provide it.

largoes · Feb 24, 2025

Since your SPF, DKIM, and DMARC records are good and there’s no blacklisting, the next step would be to check the email headers from the bounce-back message for more details. Sometimes, the receiving server provides clues about why emails are being rejected.

DediRock · Mar 7, 2025

It sounds like the recipient’s mail server is rejecting the emails. Check if your IP is on any private blocklists, ensure your reverse DNS (PTR) is set correctly, and try contacting the recipient’s IT team for more details.

Harry P · Mar 17, 2025

AlpineHost said:
I have a customer in the US that is receiving a "host relay3.domain.com[IP Address] refused to talk to me: 554 relay3.domain.com" error on emails sent to his US Government email address and a few other domains, from our Plesk server. We have done an IP check on our side and we are all good, no blacklisting anywhere. SPF, DMARC and DKIM records are all confirmed to be correct. What will be the next step to check? Or, is this something that the customer needs to figure out on his own?

Your setup seems fine, usually, this error is about missing or incorrect reverse DNS (PTR) records or strict filtering on the recipient’s server. Double-check your PTR record matches your mail server domain exactly. If that’s okay, the next best step is contacting the recipient's IT team directly to ask them to whitelist your IP or domain.

DemoTiger · Mar 25, 2025

I think the error email doesn't contain much information and is failing on some recipients using a particular type of firewall/security system, not all the recipients.

Aaron Lavers · Aug 8, 2025

AlpineHost said:
Hi all,

I have a customer in the US that is receiving a "host relay3.domain.com[IP Address] refused to talk to me: 554 relay3.domain.com" error on emails sent to his US Government email address and a few other domains, from our Plesk server. We have done an IP check on our side and we are all good, no blacklisting anywhere. SPF, DMARC and DKIM records are all confirmed to be correct. What will be the next step to check? Or, is this something that the customer needs to figure out on his own?

Thank you guys in advance for the feedback.

What you've already done right:
- No blacklists
- SPF, DKIM, DMARC are correct

Next things to check:

PTR record (rDNS): Your sending IP must have a valid PTR that matches your mail hostname.
→ Use:

Code:

dig -x your.ip.address

EHLO/HELO hostname: Must be a proper FQDN and match the PTR.

STARTTLS support: Some servers (especially .gov) require encrypted connections. Make sure your mail server supports TLS.

IP reputation (private lists): You might be blocked by internal policy filters (e.g., Microsoft SNDS, Cisco Talos), even if not on public blacklists.

Contact recipient domain: If everything looks good, ask your client to have their mail admins whitelist your IP.

Hope that helps!

Mujkanovic · 2026-08-02T07:50:53+0100

Worth pinning down where in the SMTP conversation that 554 actually lands, because it changes what is worth checking. If it comes back on the opening banner, before your server has even sent MAIL FROM, the far side is refusing the connecting IP and has not looked at SPF, DKIM or DMARC at all. Auditing those records will not move anything in that situation, which may be why everything on your side keeps checking out fine.

Open a connection by hand from the sending IP to their MX on port 25 and watch each stage. A rejection on the banner points at IP or rDNS policy, one after RCPT TO points at rules on the recipient side, and one after DATA points at content filtering. Three different problems, and three different people to talk to about it.

Plesk customer email issue

AlpineHost

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NizhalHosting

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AlbaHost

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largoes

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DediRock

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Harry P

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Mujkanovic

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DemoTiger

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Aaron Lavers

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Mujkanovic

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