After installing service pack and latest patches encountering problems sending emails.
In e-mail manager, creating a new or opening an existing  outgoing mailbox  gives the following error
"No MBC found implementing interface 'MBCI_TRANSFERDIALOG' for subclass 'EMAILSendSite:0'

Error indicates that required MBC is not present and not registered. Ideally whenever EMAIL connector is installed, this MBC gets copied and registered.

At this point of time follwing is recommened:
1. Using installer server, re-configure EMAIL connector. This will re-register all the MBC again
Once done check if the reported issue still exists.

In case issue is not resolved then unistall EMAIL connector [as well its patches] and re-install it again along with latest EMAIL patch. Please make sure that you take backup of your integration prior uninstalling the EMAIL connector.