Gliffy is sending soooo mannnnnyyyy emaillllssss it has totally minimized the happiness this feature brought initially.

The very same issue also applies to the Draw.io plugin

See also this question on Atlassian Answers: Draw.io for Confluence sends notifications each time a file is saved

There is a minor edit flag on attachment changes that could be used to disable this, but it's not working in Confluence 6.x, see https://jira.atlassian.com/browse/CRA-1491. The current latest comment there does suggest a workaround:

we disabled the notification on attachments updates completely by disabling the following modules of system plugin "Confluence File Notitication":

file-content-update-notification

file-content-remove-notification

Workaround but no angry spammed users anymore... This workaround was approved by Atlassian support.

Only possible with own server.

To give you a use case and the most important reason for my request, we are using the Gliffy plugin.

The very same issue also applies to the Draw.io plugin (running Confluence 6.0.3 and Draw.io plugin 6.3.4.1).
Every edit on a draw.io diagram produces an email notification - regardless of the configured batch notification window.
An improved behavior would be very much appreciated!

To give you a use case and the most important reason for my request,
we are using the Gliffy plugin. People tend to save their work every minute to not accidentally loose their work. This triggers a lot of emails.  (also given that every Gliffy drawing is stored as 3 attachments, so we get 3 notiifcations per any "Save" of a Gliffy drawing.)

Having this feature completed, so new revisions of existing attachment will be included in bulk emails instead of immediate delivery, would be a great advantage!  Getting rid of this amount of email "spam" would increase productivity of many people.

Please complete the "bulk email" solution therefore ASAP.  (Please increase the severity if it helps for earlier consideration)  By the current priority I'm afraid that Atlassian will never do it. After all there are other suggestions and bug fix requests in the queue for 10 and more years....

please consider this request for early delivery; I wonna ask you to get this feature added to the 5.10 code stream, as we have no plan for the next 12 months at least to migrate to 6.0.

In the meantime you should also add a clarification to the release note that the bulk notification feature does currently only work for pages, not for attachments.