Mac Mail Constantly "Downloading Messages"

Also having this problem with Yahoo Account in Mail with my Macbook Pro 10.13.3, High Sierra.

I was actually installing the yahoo account when this started, then I went to check my other Mac and there was with the same problem, always downloading emails, thousands of emails non stop. I thought it could be because of iCloud but the Mail program was not included in iCloud, I didn't do it because it would take too much space on the server and I didn't have that space. No extra storage.

Conclusion, I have been busy for about 3 days for many, many hours doing research on google to find a solution, so far nothing worked, it was messy I can say! I managed to stop the downloading but then it wouldn't receive email, only send. Also had the situation that it would stay offline giving Authentication Failed, had Login Failed, etc...........

Now back to the start. Mail still downloading...........

I wish I had an answer for this problem.

On my old MacBook Pro from mid 2010, with the Mail Program off, I could find the file MessageUidsAlreadyDownloaded3 and delete from the folder Mail in Library. Exact location was in the Home folder: Library/Mail/V5/MailData/MessageUidsAlreadyDownloaded3.

Now on my new MacBook Pro I don't find this file to delete, not in V2, neither in V5..... 😟

I was experiencing this issue as well across four machines in my office. Over 30GB were unnecessarily being downloaded daily. Neither Apple nor G Suite (email provider) support was able to offer any meaningful solution.

What I eventually discovered was the issue is linked to the setting under mailbox behaviors to store drafts on the server. Changing this to store drafts "on my mac" and restarting Mail resolved the issue for me. I hope this is useful to others suffering from this issue, of which there seems to be many.

I'm not sure if this is an issue with G Suite or with Mail, or maybe a combination of both. Interestingly personal gmail accounts don't seem to be affected. Regardless it was incredibly frustrating to deal with considering email working properly is one of my most basic expectations from my computer/email provider.

Thanks AaronA36. It appears that my issue is the reverse of yours. The drafts are on my Mac (>200GB of drafts).

This started happening immediately after upgrading to High Sierra.

My actual Mail size is 35GB.

The gMail drafts on my Mac are located here:

I wish someone at Apple would pay attention to this. Just downloaded Airmail which at least manages messages and sends and receives without drama. Sad that Apple can't get this simple program right, nor is motivated to.

Just wanted to say I have the same thing. Noticed it just recently, some days after upgrading to High Sierra. Checked CPU usage by Mail, it is low so that is not a concern here. But baffling.

I have this issue. I have Yahoo and Gmail accounts. Always downloading 1000s of email. Never stops even when I don't have new mail. Looking for solution..

Sorry all... I spoke too soon... It started again about 2 or 3 hours after writing my last post 😟

Has any solution been made to this? I am having the exact same problem and am going WAY over my data allowance as a result. I am downloading 70,000 continuously every day.

Still not resolved.

I’m now down to 20GB out of 1TB on my MacBook. Should have 200GB free.

It’s also chewing up Time Machine space.

Thank you for sharing this ohne22. For whatever strange reason it did resolve the problem for me as well!

Thank you so much! This fixed everything.

Thanks!! It worked for me too!!

did you have any success finding a solution Ber?