Any instant message software for Linux email server ?

There are many GUI messengers, of which Pidgin is probably best known and most used.

There are also command line messaging and chat tools. This is an old forum thread, but it looks like a good place to start: https://www.linux.com/forums/command...mand-line-chat

I am uncertain what that question really means. Email and Instant Messaging are two totally different things. Linux repos have MANY IM servers and clients, and TONS of Email software, but IM clients do nto normally get email, and email clients do not often do IM. (There are some exceptions that are both IM and email clients, but that is rare. Two, or more, different kinds of protocol.)

If I remember correctly, under UNIX, mail could be considered instant messaging. You just send the message to USER@HOSTNAME with the mail command. But I don't think that's what the OP is asking. In fact I have no clue what the OP is asking.
@KokChong, can you please clarify?

Dear All, thanks for your response and info. I'm thinking to install a instant messaging software in our Linux email server. Maybe I should setup a IM server in a new server.

I once did a short stint with a company that had an internal implementation of Pidgin instant messaging for employee use. A web search informs me that Pidgin is just a client program. There doesn't seem to be a "pidgin" server. I don't know what server that company used, but my guess based on observing how they did things would be jabber.

A web search for "im server linux" will turn up a number of useful links. This link provides a list of possible chat server programs: https://xmpp.org/software/servers.html

As to whether to install it to your mail server or create a separate server, I suspect the most important consideration will be current and expected traffic and how muscular your mail server is. As chat is mostly text, I doubt it would be much of a load compared to HTML email, but that's just a guess.

OK, now I understand. You want an IM server, and you have an EMAIL server, you just want to expand that one server to do both. As mentioned above, as long as your server has the muscle that should not be a problem. Just install ANY IM server onto that machine, configure, and go.

I recommend using an XMPP (Jabber Protocol) server that allows for encryption of traffic. There are a TON of such servers available, and all of them are good. Pick one that is easy to configure and maintain.

EJabberd and WildFire come to mind at once as having web based management and easy install in most distributions.

That would be what I would do.
Check out openfire/wildfire for a "chat server".

we use openfire here at work with pidgin clients.