In my account (Mini), I am allowed only 5 domains.
If one uses also subdomains (as I do), these unfortunately are considered as individual domains by Runbox, which IMHO reduces the usefulness of the account.
Is there some great expense that stops Runbox increasing the quota available per account?
Hello. Sub-domains are domains in their own right even though you aren’t paying for an additional “domain” with your domain registrar. They have their own DNS records for mail delivery and as such are quite separate apart from looking similar to the domain they are a sub-domain of. All this makes them a cost effective way of having a wider range of email addresses. There is no reason why they shouldn’t be considered as domains in our system (though I can see why some people wouldn’t agree).
You can of course upgrade your account as the Medium and Max plans have different domain quotas, or if this isn’t as cost effective as you just need an additional domain (or two) then you can purchase those separately on an annual basis.
It certainly isn’t cost effective for myself to purchase additional.
Sorry to wave FastMail in your face, but in my account I have numerous domains hosted with them and I haven’t come up against any limit yet (there must be a limit but I don’t know what it is), so for email hosting they are better value (for myself) than Runbox.
If I only had a few domains, Runbox may be better value.