From address is different for each email

From mail template, email preview, each time I send a test email to myself the email domain changes.

How to make it stick to one email address?

1st email is from Blogging <no-reply@nikitas.isb.bj.edu.cn>
2nd email is from Blogging <no-reply@17eugenel.isb.bj.edu.cn>
3rd email is from Blogging <no-reply@18annc.isb.bj.edu.cn>
4th email is from Blogging <no-reply@16annettey.isb.bj.edu.cn>

This site I am testing from is http://blogs.isb.bj.edu.cn/28kaciew/.

Thanks,

Matt