how to fix daily email limit

Hello,

Are you using a free outlook.com/hotmail.com address for business purpose, or are you using a business email address (custom domain), or are you using an onmicrosoft.com domain?

If you are using a free outlook.com/hotmail.com address, you will have the strictest daily sent limit as it is not designed for business use. The actual limit number is different from user to user, depending on account usage history, credibility, etc.

Can you use the instruction here, change the email to plain text or rich text format (basically avoid the html format) and see if it goes through:

https://support.microsoft.com/office/change-the-message-format-to-html-rich-text-format-or-plain-text-in-outlook-338a389d-11da-47fe-b693-cf41f792fefa

Blocking and daily limits are enforced by Exchange Online to prevent outbound spam. When those limits are exceeded, sending is restricted until the limit window resets, or the account/domain is explicitly unblocked by an admin.

For business (Microsoft 365) mailboxes, the admin should:

1. Check if senders are restricted as outbound spam
   • In the Microsoft 365 Defender portal, go to Email & collaboration → Review → Restricted entities and see if any invoice/statement sending accounts are listed.
   • If listed, follow the guidance in Remove blocked users from the Restricted entities page to unblock them. After unblocking, restrictions are usually removed within about an hour.
2. Check for NDRs indicating sending limits or spam blocks
   • Look at the Non-Delivery Reports (NDRs) returned to the senders.
   • If you see errors like 550 5.1.8 Access denied, bad outbound sender, the account has exceeded Exchange Online sending limits and has been blocked as a suspected spam source.
   • In that case, first secure the account (treat it as possibly compromised), then unblock it:
     1. Follow the steps in Secure a compromised email account in Exchange Online.
     2. Unblock the user on the Restricted entities page in the Microsoft 365 Defender portal.
3. Verify domains and connectors if sending high volume
   • If invoices/statements are sent from an app or device using a custom domain, ensure the domain is an accepted and validated domain in Microsoft 365.
   • If you see NDRs like 5.7.750 Client blocked from sending from unregistered domain, add and validate the sending domain in Microsoft 365 and ensure any outbound connector is correctly configured and uses an accepted domain.
4. Stay within sending limits and adjust workflow patterns
   • If invoices/statements are sent via SharePoint workflows or automated processes, redesign them so they do not exceed Exchange Online sender limits (for example, number of recipients per message, per minute, or per day).
   • For SharePoint Online workflows, configure them to:
     • Send to fewer than 200 recipients at a time.
     • Use pauses in the workflow to spread sending over time.
     • Prefer sending to a Microsoft 365 group, distribution group, or mail-enabled security group instead of many individual recipients.
5. Monitor and control outbound spam going forward
   • Use the built-in alert policies such as User restricted from sending email, Email sending limit exceeded, and Suspicious email sending patterns detected to get notified when accounts approach or hit limits.
   • Use Message trace in the Exchange admin center to review blocked or spam-flagged messages and adjust processes accordingly.

If the sending pattern is legitimate but regularly hits limits (for example, very high-volume invoicing), centralize sending through a small number of well-secured accounts, keep domains fully validated, and ensure automated workflows batch and throttle mail so they remain under the documented Exchange Online sending limits.

References:

• NDR error code "550 5.1.8 Access denied, bad outbound sender"
• NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750
• Outbound spam protection for cloud mailboxes
• "Daily email limit has exceeded and your workflow has been suspended" or "Unable to send to a recipient" error in a SharePoint Online workflow
• Fix issues with printers, scanners, and LOB apps that send email using Microsoft 365