C-Command Software Forum

Mail constantly displays "downloading messages" in Activity Window

To be clear, I don’t believe that this is necessarily a SpamSieve issue, but it is Mail related, and I’m pretty stuck.

My issue: Mail always shows “downloading messages” in its Activity Window. And it appears to consume memory faster than it used to (I need to restart Mail on my SpamSieve drone every 3-4 days now; used to be able to let it run for 2-3 weeks before memory use got excessive).

I’ve posted to Apple’s Communities here https://discussions.apple.com/thread/7938953. You can find the history of what I’ve seen and done there. No responses yet.

I have gone through and disabled all mail accounts and then enabled them one by one. Hasn’t helped to narrow things down.

Any suggestions?


Have you tried a complete rebuild?

Also, are you running any other Mail plug-ins?

Michael -

Thanks so much for your response. I don’t have any other Mail plug-ins or add-ons; this is a pretty vanilla machine (it serves as our household music server and SpamSieve drone - that’s about it). I have done the “quick mailbox rebuild” thing, but not a complete rebuild. The quick rebuild of each mailbox did not change Mail’s (mis)behavior.

When I upgraded to Sierra, the Mail update caused a database rebuild (which on this machine took over an hour - lots of spam and some pretty beefy inboxes among my family’s accounts). That has made me a bit nervous about the complete rebuild (both in terms of the time it will take and then whether it will complete successfully given the volume of mail on this machine). If you think it’s worth a shot, though, and you’re reasonably confident in Apple’s rebuild process, I will give it a try.


Hi Doug,

I really do recommend the rebuild. It seems to be very reliable. You could also make a backup beforehand to ease your mind.

Again, Michael, thanks for your timely response. I tried it - “Import Failed”. Error dialogue suggests that I ensure i have enough space in my Home directory (?) and try again. There are 460GB free on the disk, so I should think that there’s plenty of disk space. I suspect a memory-allocation error of some kind (though I wasn’t watching System Activity at the time of the error).

I’ve gone ahead and deleted all of the accumulated spam messages in the accounts monitored by the Drone, and emptied the trash for each account (using the webmail client provided by my ISP). Trying again.

If this fails again, my next step would be to try to disable some of the Mail accounts, start Mail up with a subset, and then enable those disabled accounts one by one. Does that make sense, or do you have a better suggestion?


Yeah, that sounds like a Mail or OS bug.

Sounds good. Another idea would be to export some of the mailboxes and then delete them from Mail, so that there’s less to rebuild. If the rebuild succeeds, you could then re-import them later.

Okay, I sucked it up and re-built Mail’s databases from scratch. No change to the “downloading messages” behavior. The rebuild went fine after I deleted what turned out to be a problematic account (it’s “Spam” folder was apparently a mess, causing Mail to think that there were ~450,000 messages in there - there weren’t). Re-started Mail (went fine) then re-added that account (went fine). Mail and SpamSieve are operating as expected EXCEPT for the persistent “downloading messages” message.

Any additional thoughts / suggestions much appreciated. Frankly, I wouldn’t much care except for the apparent memory-leak issue. This becomes a maintenance consideration, and I travel quite a bit (often off the grid), making regular maintenance restarts tricky.

Do you still have the Downloading Messages without the problematic account added back?

Also, could you tell me how you are measuring the memory leak?

And which version of macOS are you using?


I’m inferring it from the monotonically increasing value for “Memory” in Activity Monitor. When I start Mail, the value is usually around 100MB (or a bit less). Within a couple of days, it’s generally above 600MB. Once it gets close to 1GB, I restart Mail. That used to take a couple of weeks; now it’s my sense that it takes 4-5 days.

MacOS 10.12.4
Mail 10.3 (3273)

Thanks for all of your help!!!


Do you see any particular bad effects when it gets to 1 GB? Does the Real Private Memory (you may need to tell it to show that column) also increase like that?

What I’ve seen in the past is that when Mail’s memory use approaches 1GB, Mail becomes unstable in various ways. It may hang, crash, or slow down. Sometimes the entire machine is affected (requiring a reboot). Typically, though, I restart Mail prophylactically at about 750MB and all is good.

TL;DR - Real Private Memory increases along with total memory.

I erred in saying “monotonically increasing”. Watching more closely for a bit, I see that while the memory use trends steadily upward, it’s more of a sawtooth pattern.

As for memory consumption, here is a brief log for the past 18 hours or so:

Time Memory Private Memory “New Messages” count in Downloading message
Tu 12:40p 115.7MB 91MB 150 new messages
Tu 16:00 150MB 124MB 407 new messages
tu 23:15 220MB 186MB 712 new messages
W 6:45a 297MB 250MB 934 new messages

I figure I’ll have to restart Mail by Friday, when the new message count should be well into the 1000s.

I guess there must be something else going on besides a leak, because although 1 GB seems excessive for a mail program, the system should definitely be able to handle allocating that much to a single app.

Resolved by Sierra update 10.12.5
While upgrading to Sierra didn’t fix the problem, it appears that the 10.12.5 update does the trick. Both the persistent “Downloading Messages” status AND the apparent memory leak are gone.

I’m glad to hear that. Thanks for the follow-up.