On Outlook for Mac version 2016 connected with IMAP to a Kopano server, you might experience the following:
The total attachment size exceeds the limit. Try removing one or more attachments before saving or sending.
Googling this gives two results, one from a Microsoft “independant advisor” and another from Superuser.
Superuser has advice on deleting large attachment. It seems that Outlook has an issue with large attachments. We’ll leave the instructions on how to delete large attachments here. The Microsoft “independant advisor” leaves advice about clearing the cache for a folder by right clicking. But the Microsoft advisor makes the spurrious assumption that the end-user is using Exchange. The user replies repeteatedly, saying there is no right click menu. Not everyone who uses Outlook uses Exchange by the way. We’ll leave a link to that article.
How to clear up space in Outlook Mac for large attachments (copied verbatim from Stack):
- Select your mailbox, tap on the Outlook Search bar
- The search ribbon opens up
- Click on attachments –> greater than 10 MB
- This will open up a search bar. In that change the size from 10000 to 30000 (depending on your attachment size)
- In the search ribbon change the selection to “All Mail” – 3rd button from top left in the ribbon or ‘All Items’ to get the results from all the Outlook items.
- Right click on the message, click Attachments and Remove All. Once done, check if you can reproduce this error message.