Why can I not Forward some large size emails yet I can receive them

Hi,

When you get a big email, Microsoft 365 just keeps it stored safely on the server, so receiving isn’t usually a problem. The trouble starts when you try to forward it, Outlook has to re-upload that whole message and its attachments through Microsoft’s outgoing mail server, and that’s where limits kick in. Even though Microsoft 365 allows up to about 20 MB per outgoing message, attachments grow a bit in size when they’re sent (thanks to encoding), so that 17 MB file can suddenly tip over the limit and trigger the "file too large" message. Sometimes the recipient’s mail system has an even smaller cap, some still stop at 10 MB, which can also cause Outlook to complain or stall. And occasionally, Outlook itself just bogs down while syncing or uploading, especially if the network’s a bit slow or cached data gets in the way. On top of that, antivirus tools or mail-scanning add-ins can interfere too, quietly blocking big attachments while trying to "help."

A few tricks usually help get around this issue. One easy fix is to use "Upload to OneDrive" instead of sending the attachment directly, Outlook will turn it into a cloud link, which keeps the email tiny and skips the size limits entirely. If the file’s just a bit too large, you can also zip or compress it first; sometimes that’s all it takes to slip under the cap. Another simple workaround is to forward it as a link, just save the attachment to OneDrive or another cloud service and drop the share link in your message. And if none of that helps, it’s worth checking whether your antivirus or an Outlook add-in is slowing things down or blocking large attachments , a quick temporary disable can confirm if that’s the culprit.

Kind regards,