Email Activation code no longer sent

(Epicollect5 - Usk CaSTCo Citizen Science)
Castco Citizen Science Project
Helen - Manager on the above project is not longer receiving the Activation Code - please can you rectify this as she needs access to add on new locations.

It appears that an address with the domain “w*****” has been bounced with the error

“Not Delivering to Previously Bounced Address”

This error indicates that the email address is currently suppressed by our system from further delivery attempts. Why? Because during a previous delivery attempt to this mailbox, the recipient’s email provider returned an error to us indicating that the mailbox/email-address does not exist, or is invalid for some reason.

The error received is " User unknown in virtual mailbox table"

Please make sure that issues with the domain w***** are resolved before trying again.

HI. Afew weeks ago we swapped websites over and this affected external emails. The emails are working again. are you able to do something your end to ensure Helens email is recognized by yourselves again?