[TYPO3-english] Reverse proxy breaks backend URLs

[Glenn S]

Hi,

I'm running TYPO3 7.6 behind a reverse proxy (nginx proxy_pass).

I've figured out that I needed out to add a domain record to my site to make it display.

However, lots of image links in the backend are broken. These URLs point to the internal hostname of the machine that TYPO3 is installed on (which is not visible to the internet) rather than the external domain name that the user types into the browser.

Examples of what is broken include dotted lines in the backend page module and images in the rich text editor.

I made a Stack Overflow post about this a while ago, but haven't got a (complete) answer. I'm not allowed to link to the post because of this forum's spam protection, but the title is "how-do-i-tell-typo3-what-its-url-is-when-using-a-reverse-proxy".

Any help would be much appreciated.