After I updated my Mac to Mojave, the mail app became very slow, particularly with the rules.

I have rebuilt mailbox, restarted Mac and Mail multiple times.

My account connects to MS Exchange.

It takes ages to open rules, scroll down and add new senders to a rule I have created to mark "spam" and move all emails from this sender to junk folder. I have checked today, and to run the rule on one email takes about 1 minute. Any ideas?

  • I had no end of problems with Macs and iOS devices using Mail.app to connect to Exchange servers. Finally, out of desperation, I started using and recommending Outlook. The problems went away. YMMV and you may not like Outlook (I sure don't) but you will have all sorts of problems with Apple Mail connecting to Exchange. I have no idea why but for most people Outlook works better. Also a long list of senders to mark as spam is a recipe to slow down any email app. Mar 7 at 0:07

2 Answers 2


The way you are blocking Spam recipients is not recommended. Adding lots of single rules will slow down your Email client. Instead, enable the built-in Junk filter feature or use a Third-Party tool e.g. SpamSieve


I've had the same issue for Mojave and now Catalina. I've posted several 'suggestions' to Apple for improvements, especially the clunky UI, but nothing's come through yet!

The only way I know to speed things up is to move to a new, identical rule once the number of conditions grows to over 100, otherwise the interface just gums up.

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