Update 3/31/2026: High Volume Email is now Generally Available (GA). Please see High Volume Email Is Now Available in Exchange Online.
High Volume Email (HVE) for Microsoft 365 enables customers to...
Updated Mar 31, 2026
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High Volume Email: Continued support for Basic Authentication & other important updates
As a replacement Basic Auth it's fine except it seams there's a 10MByte email size limit. Understandable in the original role but too small for MFDs. Is there any way to get around this?
Simone_Liebal
Microsoft
MicrosoftHuw_w while HVE will continue to support Basic Auth until September 2028 (alongside support for Modern Auth), the main focus of HVE is around High Volume Email scenarios. That being said, we have heard the feedback around the 10MB email size limit and are looking into it!
There's no mention of the 10MB limit in the GA announcement?
- Nino_Bilic
Please see documentation for service limits: Manage High Volume Email for Microsoft 365 | Microsoft Learn
I think Huw_w's concern is that the 10 Mb limit is too small for many of the internal use cases. One particular use case for my Firm is "scan to email" from multi-function printers that cannot support modern auth. In this scenario, office workers are scanning large documents into PDFs and these PDFs are being emailed internally. If there is a limit on attachment size, it should match the policy of the organization as established in Exchange.
