When attempting to send emails to a large group of recipients, it is best to ensure the following:

1. Check your email provider’s sending limits to confirm that it is possible to send emails to a large group of recipients.
2. Check your email settings to ensure that the email is copy-able or BCC-able.
3. Make sure that your emails are going to valid emails addresses and that they are not outdated or incorrect.
4. Make sure that when communicating with a large size of recipients, it is recommended to break up your list into smaller groups.
5. Check to see if your IP address has been blocked for suspicious or spam activity.
6. Double check your email content for any potential spam trigger words.