Have you received an email like the below?
The reason you have received this email is that a customer has directly emailed your Collins Mail address (firstname.lastname@example.org) without entering the DMN reference number in the subject line of the email.
They have most likely done this by copying the email address from any previous correspondence you may have had with them and pasting it into a new email chain. By doing this (as opposed to replying directly to previous messages or without including the DMN reference number in the subject line), Collins cannot link the message to a booking. Collins Mail works by storing emails against individual bookings and the absence of any reference number will result in the email being forwarded on to the designated inbox entered in the “Forward unknown Collins Mail messages to” field (see guide).
The designated email address that unlinked emails should be forwarded to can be set up/changed by heading to:
Settings > Venue > select Venue > Emails & Texts > Forward unknown Collins Mail messages
The forwarded email (such as the example above), will contain the main body of the email and also importantly, the email address of the sender. With these two pieces of information, you should be able to cross-reference bookings in your system and work out which booking this should be linked to. You can then compose a new message within the booking and continue communication through Collins.