Apprended below is a Member Notice that I created for my group to provide clarification on how attachments and photos work in groups.io. I keep this on hand to send to any individuals who need an occasional refresher.
Most of this is configurable....
-- Total storage allocation is based on your group payment plan. Free groups are limited to 1GB as indicated...you can upgrade to 10GB for $10/month.
-- What the system does when you reach your total storage limit can be changed at Admin->Settings->Message Formatting->Out of Space. I have our group set to "delete old attachments." I believe most people will find this preferable to the alternative (bounce back the messages).
If your group is bouncing back emails with images in them this may be why.
-- You can set a maximum size per photo at Admin->Settings->Photos->Max Size in Email and ->Max Size in Photos Section. I have ours set to 2048px, mainly to keep a few over-eager individuals from using up all our storage (it happens).
-- Finally, as Duane mentioned, you can set a limit on the size of attachments in an individual email at Admin->Settings->Default Sub Settings->Max Attachment Size.
Be advised that this last setting may not work the way a lot of group owners think it does. First, the system will take any image over the size limit (2048 px in my case) and downscale them. Then it adds up all the attachments in the email. If that TOTAL is over the limit (5 MB in my case), it sends hyperlinks instead of the original photos. So if your subscribers want their photos to get through unscathed, they'll have better luck sending one image per email instead of 20 images in one email...assuming you have any limit set here at all.
Also note that such hyperlinked images will not be viewable online until your subscriber logs in. Users generally expect to be able to click on a link and be taken directly to the image, and are often disconcerted when it doesn't work.
There are other settings for images in databases and the wiki which probably aren't relevant to your problem.
Hope this helps,
Bruce
Here's that Member Notice:
Just some notes on file/photo attachments and uploads in the new GROUPNAME at groups.io.?
Files in general:?
-- All files and photos, whether uploaded or attached to emails, count against our total storage allocation (currently 1 GB).
-- Once we reach our limit, file attachments to emails will be deleted (oldest first) to remain under quota.
-- Files and photos in member archives can only be deleted manually.
-- Each file in "permanent" storage shrinks the email-attachment queue by a corresponding amount.
Photos specifically:
-- All photos are resized to 2048px or smaller in the longest dimension. This should be more than adequate for viewing online.
-- If you are concerned about loss of quality by being rescaled by the server you should do so yourself before sending.
-- Those with a real need to share print-quality images should upload them to cloud storage and send a link instead.
Email attachment limits:
-- Some email servers will refuse to deliver emails if they get too big.
-- To keep emails from bouncing, if the size exceeds 5 MB, hyperlinks will be sent instead of attachments.
-- The linked files/photos are still stored on the server and still count against our quota.
-- Because they are stored on the server, you can't view/download them without logging in.
Bruce