Why are e-mails from legitimate server not received

Spam has been and still is a very annoying issue. It’s better managed nowadays by having multiple blacklists of known “spammy” IPs, better email server configurations and more aggressive spam filters. This also raises the requirement levels that legitimate email servers must adhere to.

I have a legitimate mail server that is used by several domains. I know that it has been properly configured at a server and DNS level. The problem is that some emails that my clients are sending are still flagged as spam by some ISPs and email providers. It can get even more confusing when you don’t have any clear answers to this in your servers log files, meaning that you have to assume that the problem is on the receiving end. To be more specific :

  • receiving Yahoo addresses marked emails as spam
  • receiving Outlook/Hotmail addresses were not receiving my emails at all

The email filtering for the companies mentioned above simply didn’t like my e-mails.


Reasons why are e-mails from a legitimate server not received

In my setup I have assumed that everything has been properly configured. In case I would have missed something or my assumptions were wrong, the following are worth looking into :

  • Mail server DNS records
  • Client domain name records
  • DNS record propagation
  • Domain age and reputation
  • Blacklisted e-mail server domain has been
  • Receiving-end content filtering

Workarounds for e-mails not being received

For some e-mail providers (Microsoft in particular with the Hotmail/Outlook service), my e-mails were not being received at all, regardless of my settings. E-mail filtering and handling is handled differently, which can vary from provider to provider. It can be hard to pinpoint the actual reason why e-mails are not being received, because you have no clear knowledge of whats happening on the receiving end. The following will help you or your correspondents receive e-mails and will help spam filters self adjust in order to recognize your server as legitimate.

  • check the spam folder and if the e-mail ended up there, mark it as not spam – this way filters will get updated and will not treat it as spam in the future
  • add the e-mail address to the receiving address contact list 
  • verify your content – usually when testing my email server I use short / random texted e-mails. This might be interpreted as spam by some filters. E-mail marketing companies know better on this subject and I recommend their advice on avoiding certain words in the subject line and e-mail body.
  • use e-mail filters – instruct your provider to receive e-mails from certain addresses in the Inbox folder
  • wait for your e-mail servers’ domain name settings to be updated and propagated worldwide – domain name providers usually tell us that we should wait up to 72 hours for DNS records to fully propagate. It usually happens faster and we could check using online tools.



Most of the above are collected from what major providers are telling us to do. Assuming that your server is properly configured and you are still having problems with others receiving your e-mails, there’s not much to do except for the above, as the providers are not offering too much information on this subject.