O365 / Exchange 2010 : Hybrid - attachments missing

[CapnPugwash]

Hi,

 

O365 / Exchange 2010 in Hybrid config

 

Emails sent with attachments from on-premise Exchange to O365 account have attachments replaced with two txt files:

one called msg-xxxx-xx and one called a variant of r1,c1 etc.

 

If the same email is sent to a non O365 address , the attachments arrive without issue.

If an email with no attachment is sent from the on-prem to O365 it arrives without issue.

 

NOTE : we had this working great but we've just changed our ISP and domain hosting company.

[sukh]

What does the attachment message contain?