If you ever receive an error like the following in your MassMailer Outreach, it means that you have already exceeded your monthly email limit. Please send an email to support@massmailer.io if you want to upgrade your email plan or just go with an email add-on just for the current month.
You have uncommitted work pending. Please commit or rollback before calling
and
{"errors":[{"message":"Maximum credits exceeded","field":null,"help":null}]}