What is the maximum email size and attachment I can sent out at a time?

The maximum size for emails, which encompasses both the message and any attachments, is 50 MB.

You can attach as many files as you wish, provided they do not surpass the 50MB restriction. 

This limitation is applicable across all connection types, whether the user is accessing the service through the webmail interface or using an email client like Outlook or Thunderbird via POP/IMAP.