All messages are forwarded from Gmail to Trengo, including all spam emails.
We need to check regularly if there are any messages in the Spam folder that are not considered spam.
See below how to proceed.
Go to Inbox and click on Spam
A list of spam mails will be available
Go through the list of mails and check if there are any that should be removed from the spam folder
If yes, select the email, click on the 3-dot menu and select "Unmark as spam"
After checking, move your mouse next to Spam (see arrow) and select maximum 50 mails at a time to remove
NOTE: Assigned Out of office, BOL.com messages etc can be labeled as Notification/No reply mail