Go to your back office > Dashboard > Settings > Order email settings and click on the checkbox in front of "Please confirm that you have added Este endereço de email está protegido contra piratas. Necessita ativar o JavaScript para o visualizar. and Este endereço de email está protegido contra piratas. Necessita ativar o JavaScript para o visualizar. to your email's White list to ensure email delivery."
Make sure you add those email addresses to your Inbox's White list.

Set "Enable Custom Invoice number: Yes"
Use these options to construct your order numbering:
Y - the current year in 4 digits
y - the current year in 2 digits
m - the current month in 2 digits
d - the current day in 2 digits
n - the subsequent number of the invoice for each day
Please use "n" as a mandatory option to avoid Order number duplicates which will create problems.

Make sure you "Save" the settings after you are done editing.