Does anyone know if it is possible to integrate Mailchimp allowing me to send a group email?
I don’t know, because I don’t use email within Manager.
However, just want to advise you that as an email administrator that provides email services to clients, I and a number of other email admins filter our email systems to put into spam any emails sent from Mailchimp and various other bulk senders.
Mailchimp in particular I have found to be the worst offender for sending unsolicited emails (junk email) so you may find a lot of your emails from Manager going into people’s spam folders. Use any bulk mailer other than Mailchimp if you have to use a bulk mailer service. Mailchimp are the worst offenders and you are very likely to find your emails going to spam.
However, I would highly recommend that you use your own email server for sending invoices etc so you don’t end up having your emails go to spam as your company name is unlikely to be on any blacklist and won’t be filtered on the basis of bulk mailers.