You are currently viewing the Spectrum Community Archives
This content may be outdated or inaccurate
All posts are closed and commenting has been disabled

If you have a question or comment, please start a new post (registration is required)

Leave the Archive

Email Bouncing - anyone else seeing this problem , error code AUP#In-1300

HikerLT Posts: 2 Spectator

Is anyone having issues sending to addresses from Exchange Online? It started for me around 9:30 AM on Saturday.

We get these bouncebacks:  

Your email couldn't be forwarded from [removed my email address for security] to another email address.

Your message was rejected by the recipient email server. Please check the recipient's email address and try resending your message, or contact the recipient directly. For more tips to help resolve this issue, see DSN code 5.1.0 in Exchange Online - Office 365. If the problem continues, contact your email admin. gave this error: blocked. Please see for more information. AUP#In-1300

I contacted Spectrum tech support, and they said to send a blank message with title "unblock" to, and then to allow up to 72 hours for it to be fixed.


  • Lyn_T
    Lyn_T Posts: 466 ✅ Verified Employee Moderator

    Good evening @HikerLT

    Thank you for reaching out to us about the message you are receiving when trying to email to This particular error message means:

    "Spectrum limits the number of concurrent connections from a sender, as well as the total number of connections allowed. Limits vary based on the reputation of the IP address. Reduce your number of connections and try again later."

    If this error message is not cleared after 72 hours and you are using our email addresses within the guidelines listed please let us know. - Lyn

  • WegnerIT
    WegnerIT Posts: 1 Newcomer

    Same issue here. are published O365 exchange address's

    Office 365 URLs and IP address ranges - Microsoft 365 Enterprise | Microsoft Learn

This discussion has been closed.