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bobm's avatar
bobm
Occasional Reader
Oct 03, 2025

One 365 mailbox and several non 365 mailboxes

I am trying to configure the situation where I have one user on a microsoft 365 subscription and several other users on the domain using IMAP.

I have configured the domain to send emails to the 365 subscriber and that works.  However I am battling to get emails to the IMAP users.

I have set up connectors to and from 365 and they validate correctly.

However when I try to send a message from outside to one of the IMAP users I get 

Diagnostic-Code: smtp;554 5.4.14 Hop count exceeded - possible mail loop ATTR34

On researching this there are various tutorials which suggest loading exchangeonlinemanagement, connnect to the domain and execute Start-EdgeSynchronization

I then get an error telling me the command is not recognised.   Having searched it seems this command is only for on premises exchange servers and not the on line subscription model have.

Any pointers to where I am going wrong would be gratefully received.

exchange online

1 Reply

  • Zohaib_Yousuf's avatar
    Zohaib_Yousuf
    MCT
    Oct 04, 2025

    Hi bobm​,

    could you please share your environment details? if you have hybrid environment with Microsoft Exchange Edge server than this command Start-EdgeSynchronization will work on edge server. 
    The Start-EdgeSynchronization command you found is only for on-premises Exchange Edge servers. It won’t apply here because you’re in a cloud-only + external IMAP setup.

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