My user account had outgoing mail blocked. The day before it was blocked I sent around 7 emails total. They mostly had attachments, and the total size of all attachments was around 5MB. (Previous days had fewer emails). 

I am using the free plan, which I believe is limited to 250 emails and up to 200MB sent per day. 

I have unblocked my account, but can someone please let me know why my account was blocked when I was nowhere near the limits? I want to make sure it does not become blocked again as it is a real pain.

Thank you.