I am using version 3.3.x and I can see that OJS is saving the logs of each SMTP mailing to the ‘email_log’ table in its database. I don’t know if there is a UI to view these logs. If so, I don’t know him. However, the logs can certainly be viewed at the OJS database level by accessing the email_log table. For example, to search for correspondence to a specific recipient, you could use the following SQL query:
SELECT * FROM 'email_log' WHERE 'recipients' REGEXP '<part-or-all-of-the-email-address-you-are-looking-for>' ORDER BY 'date_sent' DESC;