E-mail generated by Hesk are considered as SPAM

[steraffi]

Script URL: http://185.58.193.30/support
Version of script: 2.8.2
Hosting company:
URL of phpinfo.php:
URL of session_test.php:
What terms did you try when SEARCHING for a solution:

Write your message below:
Hi; I use your script to manage a technical support only via mail, without allow customers to use the web portal.
It append that some mail sent by me through the script are exchanged for SPAM message, and deleted by the mail server of destination.
I suppose this trouble could be caused by the header of the mail.
Could you suggest me if there is any solution to this issue?
Thank

[Klemen]

There are several things that can be causing this and it's most likely not something in the header.

I combined many advice that has already been published in the forum into this new HESK Knowledgebase article: Email are marked as SPAM