I have Gmail integrated with Monday and am able to email customers in my Contacts board individually, however for some reason I am unable to send bulk emails to customers - i.e. the icon is absent from the menu (see screenshot).
This feature is only available on Pro and Enterprise plans that include the CRM product.
I believe it may be a gradual rollout as well, so if you do have one of those plans and the CRM product, you might want to contact monday.com to ask them to prioritize rollout to your account.