When I add an custom config like smtp_bind_address = will it get overwritten with future updates of postfix? How can I keep it?
put simply, if the services are reconfigured, yes your custom config will get overwritten, it is possible to keep custom changes, but that has it's own potential drawbacks... see here: https://www.howtoforge.com/communit...nfiguration-with-ispconfig.68554/#post-325893
And to complicate things, the answer is of course, "it depends." For postfix settings, ISPConfig sets and manages some settings, but doesn't touch others. The example you mentioned, smtp_bind_address, is not managed by ISPConfig, so if you set it, it will not be overwritten - currently. It's possible that "future updates" would affect it though, eg. there are feature requests related to utilizing specific ip addrs and certificates for client domains which could conceivably utilize that setting. As for other settings 'like' that one, it of course depends specifically what you are referring to. You can see most of what is set in the postfix install template; there are some settings changed right in server plugins without regard to the template, eg. when switching from amavis to rspam, and a few other config changes. I suppose download the install tarball and grep for each setting you have in question is the safest way to see if ISPConfig touches it.
