What Does This Error Mean?
This error means Microsoft has blocked outgoing email traffic from your account because the IP address it is sending from has a low reputation. According to Microsoft, this most commonly affects new customers and trial subscriptions on Microsoft 365. Microsoft
Important: This Requires Admin Access
This error cannot be resolved by a regular user. Only an email admin in your organisation can fix it. If you are not the admin, forward this article to whoever manages your Microsoft 365 account.
How to Fix It
If you are on a Microsoft 365 trial subscription:
Contact Microsoft Support and request an IP address exception. Microsoft will grant temporary access until you assign proper Exchange Online licenses to the account.
To contact Microsoft Support as an admin:
Log in to the Microsoft 365 Admin Center at admin.microsoft.com
Go to Support > New service request
Explain that you are receiving error 550 5.7.708 on a trial subscription and request an IP exception
If you are on a paid Microsoft 365 subscription:
A paid subscription receiving this error may indicate a reputation issue with your sending IP. Contact Microsoft Support via the Admin Center using the same steps above and reference error code 550 5.7.708.
After the Error Is Resolved
Once Microsoft has lifted the block, reconnect the affected mailbox in Smartlead:
Go to Email Accounts in Smartlead
Find the affected Outlook or Microsoft 365 mailbox
Click Reconnect and complete any prompts
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