Is this normal behaviour?

[ante.allah.fjante51]

Resource Limit Hit!
This site has exceeded its resource limits for the past hour, web traffic has been restricted.
Limits are reset every hour, please try back shortly.
Common reasons for this error:
High resource usage scripts.
Poorly coded scripts.
Time to upgrade.
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happens everytime a user registers. (Email verification via smtp)
that would be, everytime the server tries to send a mail.