Thank you wolstech, that makes a lot of sense. I'll try doing that and report here in case it doesn't work (or just edit the message if it does). Sorry Bailey, I assumed otherwise based on namecheap and miwilc's message, my mistake. EDIT : It does work and without any issues so far! Thanks again for all the help. (28.12)
That's your mail client adding that as a security measure. Some clients do it, some don't. It usually appears when the rDNS of the sending server does not match the domain in the From header. Since you're on a shared server, the rDNS will resolve back to servername.heliohost.org. If you set the From as something@tommy.heliohost.org you wouldn't see that since the domains would match. Gmail is probably the most widely known one that does this. The idea behind it is to help users in scenarios where someone makes the From address something nefarious such as update-your-account@paypal.com, the via is there to make it easier for users to see it's phishing and did not actually come from PayPal.