How to resolve Slow Email Opening on macOS Monterey 12.4

Here is what worked for me today 6/26/22 (OS Monterey 12.4 on iMac). I went into Mail>Preferences>Privacy and unchecked "Protect Mail Activity." I made sure "Hide IP Address" was checked. Suddenly all my emails will open. It was taking 1-2 minutes or more every day since the last OS update. What a relief. I hope this is useful for you.

In Primary Admin, I removed the accounts restarted and added back, no change.

I logged out of Apple ID, no change.

I went into User Library and removed a bunch of preferences whose dates more or less coincided with the problem appearance, restarted, no change.

Next I removed the accounts, went into user Library and removed all files and folders with the name Mail, shut down, restarted, emptied trash. Added accounts back, all back to normal.

Wish I knew the specific cause, but that's unlikely to come to light.

Have you tried booting into Safe Mode as leroy douglas suggested in this first reply?

Boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

If not then do so.

In order to see what software might be causing the problem (which would be carried over to the new machine during migration) you should try to fix the problem before getting a new machine.

Download and run Etrecheck.  Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the first window that comes up so that it can get additional information from the Console and log files for the report:

Also click the About… vurron and read the info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and try to determine what's causing the Mail performance problem.

Download and run Etrecheck.  Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Additional Text button to paste the report in your reply.

Then we can examine the report and see if we can determine what's causing the slowness in Mail. It's not a glitch in Monterey because if it were, every one would be experiencing the problem and we're not.

Next time click on the Additional Text button and then paste the report in the window that opens up.

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

That being said you've installed what most of the users here consider akin to malware, CleanMyMac. uninstall CleanMyMac according to the developer's instructions. Run for a while and then rerun Etrecheck to verify that there are no files remaining with either CleanMyMac or MacPaw in the file name.

In the second report check to see if it still reports a failing hard drive under Major Issues.

Major Issues:

    Anything that appears on this list needs immediate attention. 

    Failing hard drive - This computer has a hard drive that appears to be failing.

If it still reports a failing hard drive make sure you have a full and complete backup. You might want to consider getting an external SSD, clone your boot drive to it with Carbon Copy Cloner and boot and run from the external SSD.

NOTE: be aware that at the time of purchase you bought the slowest Mac that Apple offered: 8 GB RAM and a 5400 rpm hard drive.

It would be much more expensive to try to replace the hard drive in the Mini than to get an external SSD to use. And you can take the SSD with you when you upgrade your Mac.

Have you tried the following: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

I have had the same problem, sometimes taking several minutes to load the body of the email. I tried reinstalling OS, loading in safe mode nothing worked. As a last resort, I uninstalled Avast. The mail worked perfectly. I have installed Norton 360 as my antivirus and the mail loads normally.

TLDR: "Reset" Mail app (search Google for "idownloadblog how to reset apple mail" ... my original post was deleted because of adding the direct link)

Fuller story:

I've had the exact same problem. And it was getting worse and worse (longer and longer for the email to show anything but blank). The strange thing for me was that if I clicked on Reply (even when the email showed no content) I could see the message in the quoted text. 

I tried everything on this discussion board... and everything I could find anywhere else (Onyx cleaning, reinstalling from the Monterey installer, rebuilding, everything). Nothing helped. Until this "nuclear option" to completely wipe out all Mail-related files in the ~/Library folder (again, search "idownloadblog how to reset apple mail", the actual link can't go into Apple support discussions for some reason)

I've been using Mail for 5 days with zero issues! (But it's a bit slow as it redownloads/indexes my >100,000 old mails).

One (not only) common theme in this thread and also Mail is Slow and lagging. - Apple Community

is that removing or disabling part (or all) of various Security extensions in either macOS or Mail (such as Avast, Bitdefender, etc.) often seems to solve the problem. I too have had this problem since Monterey 12.4 and it continues now on 12.6.3 (my MBP can't go to Ventura) and an iMac on 13.2. I have been running for a few days now with no rendering delay problems in Mail since removing my Sophos Home Endpoint. That did not include any Mail extensions but did include a Web Scan component. I have previously read about significant changes to the third-party Security integration hooks (and exemptions for Apple software). These problems that we see in HTML email rendering (and some have mentioned Safari as well) may be interaction between Security extensions and these changes. The problems may be more pronounced in the Apple Mail and Safari apps due to unexpected interactions between third-party security tools and the special exemptions granted Apple software.

This has been plaguing me for over a year. The 'REBUILD' did nothing to fix this, I have several types of email accounts including gmail and Mac using the apple email program and all were problematic as described above. Even though I regularly delete trash/junk, I went into the settings > accounts > mailbox behaviors and changed the 'erase deleted messages' and 'erase junk messages' to 'when quitting email' ... then quite email program and restarted and now it is back to its function from a year ago... I suspect that somehow it was not actually deleting the junk/trash and was searching a mountain of trash. This was a continuous irritation and really quite annoyed that apple did not correct this despite all of these posts for over a year.

I have been experiencing this no load thing for what seems like more than a year. Open the e-mail and take a shower, have breakfast and come back to nothing. After reading some of the discussions here I went to Mail>preferences>Privacy. I had nothing checked, so on the off chance that doing something different might help I checked "Hide IP address". Don't know why, Just know that that made the difference and now everything loads up upon opening my e-mail. Go figure.

Have fun everybody!

OK, it happened again and I think I might have a hint. A buddy suggested that I look at the console log for unusual activity when Mail freezes up like this. This is console.app and I looked at the launchd.log window. I noticed several entries that look like this:

2022-08-29 14:27:40.562004 (gui/501 [100019]) <Warning>: denied lookup: name = com.apple.distributed_notifications@Uv3, requestor = com.apple.WebKi[77517], error = 159: Sandbox restriction
2022-08-29 14:27:40.562222 (system) <Warning>: denied lookup: name = com.apple.tccd.system, flags = 0x8, requestor = com.apple.WebKi[77517], error = 159: Sandbox restriction

And I don't see these entries when Mail gets unstuck. What's interesting - and if you go back in the thread you'll see I've mentioned this before - but sometimes when Mail doesn't want to load content, Safari also doesn't want to load content, but Firefox will. This tells me that 1) it's not a network issue, and 2) there's likely some common resource that Mail and Safari both use, but not Firefox. And it seems plausible that Mail.app uses Webkit to render content for display.

So... a quick google of Monterey webkit sandbox restriction leads me to believe this is some sort of security feature, and perhaps it occasionally goes awry and hangs up.

Next time it happens I'll try going into Activity Monitor and restarting the Webkit processes and see if that does anything.