If you notice that your emails to Salesforce contacts / leads are not getting logged to Salesforce, please check these 2 places:
Email Settings: check if your email account has been disconnected from Salestrail or your sync mode is Manual / Off instead of Automatic. Whenever you change your email password, you must reconnect Salestrail to your email.
Unlogged Activities tab.
Note: Emails sent to addresses that aren't registered as a contact or lead on Salesforce will be discarded.
To avoid duplication logging, Salestrail does not log emails that have multiple matches. All of these emails are kept in Unlogged Activities, and users can choose to delete or log them manually.
To manually log an email, please follow these steps:
Tap on the email in Unlogged Activities that you want to log manually.
Assign the email to the accurate existing Salesforce contact OR create a new Salesforce Account/Contact/Lead.
And Voilà! Your email has been logged to Salesforce.