When I installed virtualmin I had initially named the server vps.site-a.com, however now I’m using a different website on the same installation (site-b.com).
Some of the people I’ve been emailing will have my emails placed in their Junk folders. Upon some investigation I noticed that the path the email takes is through vps.site-a.com and not through smtp.site-b.com
How can I setup virtualmin so that emails that are generated from site-b.com show as being sent from the site-b.com server?
Once that’s done I can look at reverse dns entries and ptr records, but for now this is the logical first step.
Well, there isn’t a supported way of upgrading Postfix.
You’re using the Postfix version available to your distro – the only way to upgrade that would be to use a version from a third party repository, which isn’t something we’d recommend.
Since I don’t think that’s the cause of the problem you’re seeing, it might be better to try and find another way to resolve that issue.
However, there are some who use third party repositories and the Postfix version from them – and while we recommend against this, you could always try it and see what happens. If you choose to try that, I’d highly recommend testing that on a test server before using third party packages on your live server
There’s likely a different explanation as to why these emails are ending up in a spam folder though.
Using shared hosting, and having all email go out via one IP address, is very common.