Recipient limit for Thunderbird.

Hello everyone,

I am a high school principal and I would like to send the same email to all the parents of the students. That amounts to 2500 recipients.

My internet service provider does not allow more than 100 recipients, and it's a huge waste of time to "Copy-Paste" 25 times each time.

Do you know of any software or module compatible with Thunderbird that would be simple enough for all teachers to use?

Thank you in advance.