Forum Discussion

PaulAdebiyi's avatar
PaulAdebiyi
Copper Contributor
Mar 05, 2024

How to Fix: 550 5.7.350 Remote server returned message detected as spam

Hello, 

 

I have an issue with sending emails from my organisation emails to other mailing servers. Anytime we send an email from our organisation, i get an auto-response of a 550 5.7.350 error. I understand that the error means the account was blocked due to some spam activities but i can't seem to find anywhere to unblock the accounts or how to fix it. 

  • Chris_Itnstuff's avatar
    Chris_Itnstuff
    Copper Contributor

    PaulAdebiyiWe had this issue and i just thought i'd put this out there.
    Turns out the client was using Starlink internet on the dynamic IP plan.
    A lot of the starlink dynamic IP Addresses appear to be blacklisted.
    It appears through repeated sending from these blacklisted IP's a bad rep was created for the sending domain. (this is why sending from alternate domains works eventually the alternate domain would also build a bad rep) the combination of bad rep and blacklisted IP = failed emails. By changing the IP to IP4 it seems a new rep list is in play and so all emails were successful for about 2 months, and now the issue occurs on both ip4 and ip6.

    The solution was to simply have a static IP on the internet connection , I'd also point out while this issue was at the main office of this client there could also be situations where staff are working from remote locations or home sending with a blacklisted IP and causing the domain name to get a bad rep, from what i can tell as long as the email is 100% clean it will still be delivered, but once you have a bad rep if anything else looks out of place the message will be blocked (as if you normally get 3 strikes but once you have the bad rep you only get 1)
     

     

    • DomP66's avatar
      DomP66
      Brass Contributor
      I'm not sure why people on that thread are discussing disabling IPv6. As long as the IPv6 addresses are correctly listed in the SPF record there should be no issues.
  • markjanbakker's avatar
    markjanbakker
    Copper Contributor
    Do you have SPF/DKIM/DMARC in place for the email domain?
    Has it previous worked without problems?
    • PaulAdebiyi's avatar
      PaulAdebiyi
      Copper Contributor
      Thank you for your response. Yes, I have all setup in the email domain and yes, it has always worked. It just suddenly stopped working about 24 hours ago.

Resources