My iMac is 10 + yrs old running macOS Big Sur 11.7.6 will not upgrade to later OS versions.

Rover58 wrote:

It is a iMac (21.5-inch, Mid 2014), updated to Version 11.7.6 of Big Sur, probably as up to date as possible.

Big Sur is as far as it can go. According to MacTracker, the latest version of Big Sur is 11.7.10. You should be able to get it using Software Update – but all that you're likely to get is a few security updates and bug fixes.

I wanted to run Outlook for my mail, as the Apple Mail won't connect any longer, but the Outlook app isn't compatible with Big Sur. I can still use Safari to connect to Outlook and my MSN mail account.

I'm guessing you ran into this, or something like it.

Microsoft (June 25, 2024) – Deprecation of Basic authentication in Exchange Online

This Apple Communities thread suggests that Apple Mail might be able to connect to Outlook email if you simply "Remove Outlook account in Mac Mail then add a new 'Microsoft Exchange' account using the Outlook email and password login" … provided that you have macOS 10.14 (Mojave) or above (Big Sur is "above"). That would be a simple thing to try.

Microsoft Outlook will no longer work with Apple Mail – Apple Communities

There's also this.

Microsoft Community – Outlook App Download for macOS Big Sur 11.1

With older versions of Office (like the one I had on my old Mac), there have been reports of Microsoft taking down activation servers so that you can't even activate them if you have to do a clean install or replace a dead Mac. But you might be in a Twilight Zone where you can reinstall Office, or parts of it, even if it is now officially unsupported. I would suggest treading lightly here as you might not want to risk breaking an existing Office installation.

Your 10+-year-old iMac is almost certainly on Apple's Vintage and Obsolete hardware list. The last update for macOS Big Sur is 11.7.10 which was released over a year ago. If your iMac is found on this compatible list for macOS Monterey, you can upgrade to Monterey v12.7.6 and can get it from How to download and install macOS - Apple Support. Otherwise, you are done at Big Sur.

Apple only supports the current operating system (e.g. Sequoia v15) and the previous two major upgrades (Sonoma v14, and Ventura v13).

Rover58 wrote:

Are old iMacs no longer supported. Some of the apps I want to use only run on later versions.

Vendors like Microsoft and Adobe have a policy of only supporting "the most recent three". As of today, those are (Ventura, Sonoma, Sequoia). Because Sequoia has only been out for a short while, you may find that some of the applications from these vendors still support Monterey. (That won't last for long.)

I believe that current versions of Firefox, LibreOffice, and the Affinity V2 applications (Photo, Designer, Publisher) will run on Catalina or later. Eventually, even vendors who support older versions of macOS will start to abandon Catalina and Big Sur, in much the same way as many have already abandoned High Sierra and Mojave.

Because technology moves so fast and developers tend to develop new apps for newer devices they simply do not develop for older technology. For this reason it isn’t a bad idea at all to upgrade your hardware about every 7 years or so to stand a fighting chance of staying current. Basically, I am saying your idea to consider a new computer is wise.

I would pass on the iMac line and my recommendation for most is to simply get a Mac Mini and an external display. You will enjoy dramatic performance improvements by doing so.

Rover58 wrote:

The iMac also runs very slow, so maybe it's time for a new one or research the best software to clean it up and optimise the performance for a little bit longer.

Your Mac has 8 GB of soldered-in RAM. You could be running out of RAM, but I'm guessing not.

My guess is that one of the main causes of your misery is your internal drive. Unless you bought a version of that Mac that included a 256 GB flash drive (SSD), your Mac has either a slow mechanical hard drive, or a slow Fusion Drive. Late 2015 was when Apple cut the amount of flash (SSD) storage on 1 TB Fusion Drives from a respectable 128 GB to a miserly and totally inadequate 24 GB. It's prime real estate, but there is not nearly enough of it; when the 24 GB runs out, your Mac is back to storing things on a slow 5400 rpm mechanical drive.

If that drive is nearly full, performance may fall off a cliff.

A solution to this might be to get an external USB SSD, plug it into one of your USB-A (USB 3.0) ports, clone your current system onto it (using Carbon Copy Cloner or SuperDuper!), and then make it your startup drive.

I would suggest avoiding "cleaners" and "optimizers", some of which may actually make problems worse.

An iMac (21.5-inch, Late 2013) cannot update as far as Big Sur.

An iMac (21.5-inch, Mid 2014) cannot update past Big Sur.

An iMac (21.5-inch, Late 2015) or (Retina 4K, 21.5-inch, Late 2015) cannot update past Monterey.

Which of these iMacs do you have? (Or, if you have a different iMac, please specify.)

rkaufmann87 wrote:

I would pass on the iMac line and my recommendation for most is to simply get a Mac Mini and an external display. You will enjoy dramatic performance improvements by doing so.

Because there have been way too many reports of the new silicon Macs having display problems (lines across ½ of the screen after about a year).

Rover58:

You can get a Mini with the same RAM and SSD plus a 32" LG monitor w/speakers for much less than the 24" iMac.

Just some food for thought.