The maximum email size, including attachments, is 35 MB and your total storage is 1000 MB per account. Each email message can only be sent to 50 people maximum and you can send to a maximum of 500 email recipients within any 24hour period.
You may increase the number of email accounts you may create via the 'Account' page in the upper right corner of your website builder -> on the left-hand menu click on 'Upgrades'.
The server ports used are port 110 for incoming mail and port 25 for outgoing mail. Note that some Internet Service Providers require a different port for outgoing mail.