I want a sentence or a statement (Polite way) to ask users to reply/repost in English (when they post in different languages) in an English Forum

Hello,

I am maintaining a forum and there are 8 languages selection option in the Forum. If any of the user posts or starts a thread with other language in an English Forum, i want to reply to them with a statement asking them to repost in English as this is an English forum, it will be easy to understand if you post in English and all others can participate in a discussion.

I need a polite statement which gives the same above meaning and that too it has to be in a way which will make someone feel that "great sentence formation".

Please help me out in forming a sentence or a statement like that.