At my company we have a saying that there are no IT projects, only business projects involving more or less IT. Every IT initiative should be owned and driven by the business. Some might object to this way of seeing things. I would expect IT people that want to keep their influence and power and business people not interested in IT to belong to this category. Upgrading the mail server software to the latest version since the current version will no longer be supported by the vendor might be used as examples of a "pure" IT project that should be owned by the IT department. But it should not. It would only be a pure IT project if the mail server was not used in the business at all, which then would question its existence and cause it to be terminated.
The main point is that someone in the business should always have the ownership of initiatives involving IT, even those needs and initiatives that have been identified and requested by the IT department (such as upgrading a mail server software due to that the current version will no longer be supported by the vendor). With the ownership follows funding and taking responsibility of the business results of the initiative and the consequences for the business if it fails (such as costs related to the inability to communicate via e-mail). If there is no ownership in the business, then the initiatives which are in fact owned by the business will always have higher priority than the initiatives owned by the IT department. So, upgrading the mail server software will be in the bottom of the priority list among other IT-owned initiatives and the mail server won't be upgraded until the mail server breaks down and hurts the business (unless someone in the IT department puts it higher up in the priority list without telling the business people that it got higher priority than their initiatives).
To repeat – there are no IT projects, only business projects involving more or less IT. These include even "boring" stuff like upgrading the mail server software.