Email delivery to btinternet always fails (522 error)

[customer-96]

I recently set up a mail server with a brand new domain.

I can send emails to gmail, outlook, private domains... but all emails to btinternet.com bounce back.

Error message:
Status: 5.0.0
Remote-MTA: dns; mx.bt.lon5.cpcloud.co.uk [65.20.0.49]
Diagnostic-Code: smtp; 522 email sent from mydomain.com found on industry URI blacklists (Spamhaus/Invaluement/ReturnPath) on 2018/07/06 20:02:31 BST, please check for a listing on these external blacklists. Postmaster cannot help you if you are listed on these systems.

Attempts to resolve:

• I have checked on every blacklist site (the ones mentioned in the error and more), and none of them list my IP address or domain.
• I have tried sending simple emails and realistic emails to multiple addresses, so I doubt it's being filtered as spam.

I have seen many similar problems on these forums, and nobody seems to have found a solution. Can anyone help?

[Andy_N]

Hi, welcome to the forums.

Can you say how you set up the mail server? What IP address are you referring to?

Not sure what you mean when you say you've tried sending simple emails and "realistic" emails to multiple addresses. Have you tried sending to one email address, a basic email with no attachments or embeded URLs?

BT use Cyren for (some of) their blocking. Have a look here :-

https://www.cyren.com/security-center/url-category-check

and

http://www.cyren.com/security-center/ip-reputation-check

[customer-96]

Hi Andy,

Mail server set up by SiteGround. They're reviewed very highly and it was seamless to set up. Mail server has the requirements set out by Yahoo (DKIM and SPF enabled).

For blacklisting, I checked the IP address of the web host server and both DNS servers, and the domain I own. Cyren also classes the URL and IP as 'n/a' and 'unknown' respectively, so not blacklisted.

That's exactly what I mean for sending simple emails - no attachments or URLs, just plain text, empty emails, forwarded emails etc

Pretty stumped!

[customer-96 · Accepted solution]

This has now been resolved.

(Seems like it fixed itself)