01-21-2017 04:38 AM - edited 01-22-2017 01:24 PM
Your ISP will manage and limit how many emails you can send - at a time - in an Hour - In a day etc.
The link below give various limits for ISPs and even if yours is not listed it will fall into the range show.
As far as ACT's email merge wizard is concerned it depends on resources of the machine and mail server if one is used. Often 150 is quoted as a reasonable number to try but it is flexible and the content of the email will have a bearing if it contains graphics and is large.
01-23-2017 08:04 AM
Alongside with ch1p's advice, I would suggest trying out an emarketing service which is designed to send large amounts of emails much more efficiently, i.e. not tying up your Outlook by sending a batch of emails, and not be affected by any ISP limitations.
Act! emarketing is included in Act v18 and above. You can send emails to up to 500 contacts a month for free. You can find some getting started videos here.