If I have a hosting account and add multiple domains to it, will the contents of one site/domain affect the others?

Say if one got banned or blacklisted somewhere would it affect the others?

Thanks.

not sure what you mean but, i would presume that each of your domains on the same account will be add-on domains using the same IP unless you specify a unique IP for each of those domains. So, if they all use the same IP and SMTP gets blacklisted by several providers, then yes, you will experience the same results for other sites. I would recommend using a unique IP for each site.

For most shared hosting you'll find that the server uses a specific IP for SMTP anyway (particularly where mail isn't on the same server as your hosting), and therefore using dedicated IPs for hosting your website won't help at all in this respect.

Whether (or how) the contents of one site/domain affect the others will depend upon how your hosting plan enables you to use multiple domains.

If you're wanting to avoid SMTP blacklist problems caused by other users of the same mailserver, I would suggest considering a VPS if it's within your budget - this will give you your own private SMTP server and therefore any blacklisting issues could only arise from problems with your site(s).

You could potentially take that further and use several VPS's for several sites - but that would only be beneficial if your sites were causing the problems... in which case there are other issues.

In terms of the sites/content being banned somewhere by some provider or organisation etc. I would guess that this is typically done via domain name rather than IP and therefore other domains pointing to the same content would need to be targetted individually (and domains pointing to different content would presumably avoid being blocked).

Let us know more details about what you're thinking and I'm sure that we can all advise you more clearly and appropriately to your situation - so far I feel that myself and Ryan are guessing a lot at what you mean, and what you're trying to do/avoid.

Yes, more details would be appreciated so we can know exactly what you want

I'm not sure if you're asking about one host and subdomains, or you have server.