A large number of my Delivra contacts are unsubscribed after Salesforce connection.

If you have noticed a large influx in unsubscribed status records in your Delivra account after you connected the Salesforce integration, it's likely that those records already existed in your Delivra account but the Delivra Opt-In checkbox is not marked for them in Salesforce.

How the Delivra Opt-in check works:

1. If a lead/contact record from Salesforce does not exist in your Delivra account and the lead/contact record does not have the Delivra Opt-In checked, no sync will occur for that lead/contact. 

2. If a lead/contact record from Salesforce does exist in your Delivra account and the lead/contact record does not have the Delivra Opt-In checked, the lead/contact record will be included in the sync and be updated to unsubscribe status in your Delivra account.