Type your mass email recipient address in the Bcc box instead of the To box when you want to send a mass email. When a recipient replies to a mass email, he/she may intentionally or unintentionally use the Reply to All option which would result in a second mass email. It will be a nuisance to the group of recipients and a burden to the system.
The email subject should clearly state the purpose of the email
It can let recipients easily differentiate between normal emails and spam or phishing emails. Otherwise, recipients may inadvertently ignore or delete the email.
Avoid sending large size attachments
Email attachment is one of the common channels for spreading computer viruses. Some users are hesitant to open unexpected attachments. Sending large attachments to multiple recipients can also create unnecessary load on email servers. Users are strongly recommended to use eBulletin channel if sending large attachment is necessary.