On a technical level I am finding some of these posts a little bit confusing. (Could just be me)
I only ever used Plusnet and now Greenby email via the webmail service. That means via a web browser, one on my PC (Edge) and now another on my phone (Opera). No spam, no problems! AFAIK I had spam filtering off in my Plusnet account. Spam filtering with Greenby is On by default (Level 3), no spam emails received yet, but it occasionally puts a few incoming messages into the Spam box*. Not a problem, just flag them as Not Spam.
If people are using email clients on their devices the situation would be more nuanced. They can use POP or IMAP. I have used POP in the past but never IMAP (so am not entirely clear about its workings).
The thing is, I would assume using a client software with POP you would either operate with no spam filter on the host and use the client software for spam control, or if using host spam filters be prepared to log on via webmail in order to check for spam in the Spam mailbox. I assume, if using, IMAP you would see the Spam box mapped to your local device.
If people are using different devices to access their email, how clear are they about how it all works? e.g. POP moves incoming messages out of the mail hosts inbox to the client device so they won't then any longer be available via webmail or IMAP (some systems do retain a copy in another user mailbox, don't know about Greenby). My understanding of IMAP is that it maps the host system's user mailboxes on the client device. I assume this would indeed interwork OK with webmail, but what if some are using POP on one device and IMAP on another - plus webmail?
* With your Greenby account email settings, accessed via the Greenby portal, at FILTERS you can choose Blocked & Whitelist for email addresses. At SETTINGS you can control the Anti Spam level. Mine was set at Level 3 ("More aggressive"). I have now reduced it to 8 ("Less aggressive").
