When it comes to emails, everyone wants to have their emails reach their recipient's mailbox, but sometimes they go to the spam box instead. There are serval factors that can impact this both on and off the server.
The following items are some things that can be checked on the server and additional articles that will be able to provide some helpful infomration on how to make and verify those changes.
The Internet uses your hostname as a label by which to identify your physical server. This should be referred to as a domain name you control and be able to resolve to the server IP address as well. A majority of the hosting provided does not create a server that will reference your domain automatically and will require you to update this infomration.
The PTR, also know as rDNS, a PTR record resolves an IP address to a domain name. The PTR record resembles a reversed A record. Configuring the PTR record of your server's primary IP address to use the hostname of your server.
If you have configured your Exim service to use a different IP address, ensure that the IP address's PTR record references your server's hostname.
SPF (Sender Policy Framework) records can help verify that an email comes from a trusted sender.SPF uses DNS entries to prevent email spoofing. If an email message uses a sender address that is not valid, SPF uses the DNS entry for the sender's domain to detect the email's header's modification.
DKIM (Domain Keys Identified Email) is a validation record that detects email spoofing. This record allows your mail server to check whether a domain's administrators are authorized to send emails from a domain. The email includes a signature that your mail server uses to verify the sender's public key in their DNS record.
DMARC (Domain-based Message Authentication, Reporting & Conformance) is a technical specification to help reduce the potential for email-based abuse. A DMARC policy uses DNS to confirm that an email message uses a valid DKIM and SPF record and that the From: header matches those records.
Please be aware, these are not the only factors that can create a result in your emails to reach the spam box, but only a few factors that can be adjusted on the servers endpoint.
Some other factors can include, but not limited to:
- IP reputation
- Domain Reputation
- Frequency of emails sent
- Content of the emails sent