Outlook for Mac 16 POP3 downloads reduced to small trickle // best practice for archiving?

Question

Outlook for Mac 16 POP3 downloads reduced to small trickle // best practice for archiving?

Johannes Contag 25

Hello,

For the last 15 years or so I've been using Outlook for Mac 16 (on a Macbook running High Sierra) as the archiving backend of my Gmail. In the last few years, I've in fact almost not used the Macbook for emailing at all but done it all online on a work computer. As a result, when I do do a bulk download every 3-6 months or so, there's always a large volume of emails to be downloaded. This has usually worked OK (Outlook would download 50-100 messages per sync) but halfway through my latest bulk download that's reduced right down to 1-2 emails per sync, or even none. I went and deleted about 1000 emails from Outlook so it shouldn't be an immediate database size issue (although the Data folder in the Outlook 15 profiles' Main Profile is 22.4GB). I tried again yesterday and again today, same issue. Does anyone have any suggestions?

From a wider perspective - at some point my old Macbook will die and with it Outlook for Mac 16. What's the best way to turn that 22.4GB dataset, which contains huge swathes of personal correspondence going back to 2001, into a futureproof email archive? (I'm hoping that's not the million-dollar question...)

Many thanks,

Hornblower409 18,575 Reputation points

2026-11-01T12:45:39.2466667+00:00

@Johannes Contag

I can not add anything to the slow sync problem beyond the excellent suggestions from Chole.

But on the long term archiving problem - Does your GMail account still have all of the old data? Or do you remove it from GMail once you have downloaded it to your Mac?

If the data is still in your Google account, I can think of two options:

1 -- Google Takeout

[External Non-Microsoft Site] https://support.google.com/accounts/answer/3024190
This allows you to export your Google data in a number of formats.

2 -- Free Thunderbird email client

TBird can connect to you GMail account and download the data into MBOX format, which can be used on a number of platforms. There is TBird release for your OS.
Johannes Contag 25 Reputation points

2026-11-03T03:38:57.0833333+00:00

Thank you - no, I've been trimmign down my Gmail regularly (Googledrive issues...) and want a more complete record in my email backup. Thanks for the suggestions though!

1 answer

Your answer

Hornblower409 18,575 Reputation points

2026-11-01T12:45:39.2466667+00:00

@Johannes Contag

I can not add anything to the slow sync problem beyond the excellent suggestions from Chole.

But on the long term archiving problem - Does your GMail account still have all of the old data? Or do you remove it from GMail once you have downloaded it to your Mac?

If the data is still in your Google account, I can think of two options:

1 -- Google Takeout

[External Non-Microsoft Site] https://support.google.com/accounts/answer/3024190
This allows you to export your Google data in a number of formats.

2 -- Free Thunderbird email client

TBird can connect to you GMail account and download the data into MBOX format, which can be used on a number of platforms. There is TBird release for your OS.
Johannes Contag 25 Reputation points

2026-11-03T03:38:57.0833333+00:00

Thank you - no, I've been trimmign down my Gmail regularly (Googledrive issues...) and want a more complete record in my email backup. Thanks for the suggestions though!

Answer 1

Chloe-V 15,075 Microsoft External Staff Moderator

Hi @Johannes Contag

I understand your concern, especially since this Outlook profile contains personal correspondence going back more than 20 years.

The 22.4 GB profile may be contributing to the slow synchronization. Large Outlook data stores can experience increasingly frequent pauses while downloading new messages, and deleting around 1,000 emails may not immediately reduce the database size.

Before making further changes, please check Window > Sync Errors for any POP or Gmail-related messages, confirm that the Mac has sufficient free storage, and then restart both Outlook and the Mac. You may also leave Outlook open and connected for several hours to see whether the download continues gradually.

Most importantly, please do not delete or rebuild the current Outlook profile until you have created and tested a backup.

For long-term safekeeping, you can export the data to an Outlook for Mac archive file:

In legacy Outlook for Mac, select Tools > Export. If Export is not available there, check the File menu.
Select Mail and any other items you want to preserve.
Save the archive as an .olm file.
Keep copies of the completed .olm file in at least two separate locations, such as an external drive and secure cloud storage.
If possible, test the archive by importing a copy into another supported Outlook installation before relying on it.

The .olm format is the supported export format for legacy Outlook for Mac and can later be imported into Outlook, where the content appears under On My Computer.

Please keep the original Outlook profile on the old Mac until you have confirmed that the exported archive can be opened successfully.

Please feel free to let me know if you have any further updates, thanks

If the answer is helpful, please click "Yes". If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-29T23:25:35.8766667+00:00

Hi @Johannes Contag

May I know if you have got any chance to check my answer? I am glad to help if you have any other questions.
Johannes Contag 25 Reputation points

2026-10-29T23:56:14.5733333+00:00

Hi Chloe,

Many thanks for your answer - I'm still working through it! I've done an OLM backup but haven't been able to open it in a free OLM viewer on my Mac (after 30 mins the wheel was still spinning, plus the temp files eating up more and more hard drive space) - my other computer is a PC, and I believe I need to convert it to PST to be readable there? Also the transfer of 17GB from Mac to PC is a bit convoluted.

Re. the actual problem - the downloading at a crawl - that's still not sorted, it's still stuck in around August just downloading 1-2 emails at a time when prompted to sync (there's still many hundreds to get through). No Sync Errors displayed, restarted multiple times, around 60GB of drive space... where to next? I'll give it more time; with all the changes and exporting etc. I haven't really given it a chance to just sit there open for a few days and download when ready. If that doesn't work - rebuild the profile? Once I've verified my OLM export is accessible?

Many thanks for all suggestions!
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-11-01T23:33:05.4133333+00:00

Hi @Johannes Contag

I wanted to follow up and see whether leaving Outlook open for a few days allowed the remaining messages to download more consistently.

Were you also able to verify the OLM archive or transfer it to the PC? I would recommend avoiding a profile rebuild until you have confirmed that the exported archive can be opened or imported successfully.

Please feel free to share any updates when convenient.
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-11-02T23:27:15.1566667+00:00

Hi @Johannes Contag

Is there any update from you?

If yes, please feel free to let us know.
Johannes Contag 25 Reputation points

2026-11-03T03:49:00.69+00:00

Thank you for following up again Chloe, much appreciated. I haven't had time yet to find something to try to open the OLM archive, so will definitely hold off rebuilding my profile.

Because nothing changed after leaving the Outlook client open for a few days, I became suspicious that the problem might be at the Gmail end; digging into the POP3 settings there, I noticed that POP sharing had inexplicably been turned off during my last big download batch. (I've read that Google is wanting to move on from POP3, maybe that's got something to do with it...) The upshot being: I was given three options there, no POP3 download, just from the date of enabling the downloading, or everything. Because I was still missing all my emails in Outlook from August onwards, I chose the 'everything' option, which by the looks of it (three days of on-and-off downloading so far!) looks like it really is re-downloading everything, and unimaginably bloating my Outlook account. Hopefully I can just select unread messages and delete the duplicates in bulk (!), since there seems to be no identify-duplicates method - also I'd be most interested in suggestions on this!!

Many thanks, and apologies for what so far looks like a Gmail garden path. (I can't tell for sure yet, because the new mammoth download hasn't reached Augst yet...)
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-11-04T01:44:30.01+00:00

Hi @Johannes Contag

Please feel free to share an update when convenient.