Outgoing emails sent from Plesk server to mail services like GMail, Yahoo goes to spam folder. How to troubleshoot?
Here is the list of most common reasons why it happens:
- SPF/DKIM/DMARC are not configured on the sender's side;
- Server's IP address is compromised and added to DNS BL;
- Message content does not match requirements for non-spam email. For example, empty message will be marked as spam;
- If sender's mail account is used for sending notifications and most of the users mark this messages as spam, there is a high probability that it will go to Spam folder for other users as GMail has learning algorithms;
How to troubleshoot
1. Use online checkers, like MXToolbox, to verify that email-validation systems are configured for the domain: SPF, DMARC, DKIM.
If some warnings are detected, verify that everything is configured properly and configure if necessary:
Check that TXT record regarding SPF validation present in domain's Home > Domains > example.com > DNS Settings:
Check the How to create SPF rule for the domain? for the details.
Check that TXT record regarding DMARC validation present in domain's Home > Domains > example.com > DNS Settings:
This policy recommends that the receiving mail server does not delete messages even if they fail to check. You can specify a stricter policy. However, note that the receiving server is free to apply its own policy to incoming mail.
Check an overview how DMARC works on this page
Note: On default Plesk installation SPF and DMARC records are added to the domain's DNS Settings during its creation in accordance with DNS Templates
Check that DKIM support is enabled server-wide in Home > Tools & Settings > Server-Wide Mail Settings :
Check that DKIM support is enabled for the domain in Home > Domains > example.com > Mail Settings :
and verify that necessary records are added to domain's DNS Settings:
Note: If external DNS server is being used for the domain, make sure that all the TXT records related to DKIM, DMARC (default._domainkey.<example.com>, _domainkey.<example.com>, _dmarc.<example.com>) from domain's DNS Settings are transferred to external DNS as is.
2. Check that domain's IP is not blacklisted - Email Blacklist Check
3. Validate content of the message that was marked as spam. Common message attributes that can trigger spam filters:
- The body of the message is empty or contains spam trigger words like:
cancel at any time
check or money order
for only ($)
free or toll-free
this is not spam
- Suspicious subject of the message, like "How to become a billionaire in 1 month"
If any means server IP was blacklisted, please contact Yahoo, Hotmail or Gmail directly or with your Internet service provider:
- Outlook/Hotmail: Common Microsoft services troubleshooting or contact form
- GMail: Delivery problem form between your domain and Gmail
- Yahoo! Bulk Sender Form - Even if you are not a bulk sender, you will need to complete the form