I have multiple email accounts in TB. Emails to my personal account arrive in that account's Inbox and Message Filters move some regular mail into folders in Local Folder. Consequently, when I open TB after a few days a bag full of messages arrive, some being moved to Local Folders and some remaining in the Inbox. The new mail sound plays as expected. This is customised using a short extract from a favourite piano concerto (about 30s long). Chances are the active folder is in Local Folders from the last session, so I change to my personal Inbox, often during the new mail sound. This causes the new mail sound to re-start, which is slightly annoying. I would prefer the new mail sound to play only when new mssages are downloaded. I've looked in the options (General and Advanced tabs) but the only setting I have found is whether to use a customised sound over the default, so I deduce that this behaviour is in-built.

I am using TB 45.1.1 and Windows 10 Pro on a DELL Latitude 3540 laptop.