The short answer is there is no simple answer to prevent your outgoing email from being classified as spam. However, these are the critical steps/best practices to achieve this in the long term.
- Guard your servers reputation by quickly addressing any issue with outgoing spam.
- Create an SPF entry for your domain
- Create / enable DKIM signatures for your domain, add DNS entries for these.
- Make sure you g_send_helo setting is correct: mail.your.server and the reverse dns of your ip address points to this name mail.your.server -> 1.2.3.4 -> mail.your.server
- Enable SurgeMail's features to prevent/detect hackers early.
- Monitor and remove your server from RBL listings, primarily by stopping any spamers sending on your system.
- Use SurgeMail's config checker - it will help with many of the above suggestions.
With some large providers you can sign up for reporting to find out details about spam reports from their users related to you. Here's the one for outlook / Microsoft.
How to define an SPF record for my domain
Add this as a 'txt' record for you email domain, e.g. example.com
v=spf1 ip4:1.2.3.4/24 a mx -all
(Replace 1.2.3.4, and mail.your.domain, with your details) This DNS entry goes into your dns server under the name 'YOUR.DOMAIN' as a 'TXT' record.
In addition you should probably add a DMARC record to tell other servers to enforce spf for your domain:
So add the dns entry: _dmarc.your.domain A 'txt' record containing: "v=DMARC1; p=reject; aspf=r; adkim=r"
| Token | Explanation |
|---|---|
| v=spf1 | Version of SPF syntax |
| ip4:1.2.3.4/24 | Allow any ip address 1.2.3.0-1.2.3.255 (change to match your own mail server ip address) |
| a | Allow any ip which matches the IP address of this domain (doing a simple 'a' lookup) |
| mx | Allow any ip which matches the IP address of a mail server that accepts incoming mail for this domain. |
| -all | Block any mail from an ip other than those listed above |