Mochahost does not impose a quota limitation on your email boxes - however the quota is set by the client at the time of the mailbox creation, so you have full control of how much space you'd like to allocate for a particular user.
If a mailbox exceeds this quote, the sender will receive a bounce back message that the quota has been exceeded. Be aware if you use IMAP or Webmail (which uses IMAP) every time you send a message, this sent message is saved directly to the server, and this will also count against your storage space. Please also realize that if you store email messages on the server, each time you check mail your email program has to parse or read, the listing of messages, then grab those not already read. Eventually, depending upon your mail program, you would reach a limit where the mail program will timeout before you could download mail from the account, and this is not dependant on your connection type or speed. For this reason Mochahost support does not recommend setting mail programs to leave a copy of messages on the server, although if you still decide to do so, it is advised that you set the program to remove them after a certain period, so that you reduce built up mail in the box.
As for attachments, Mochahost does not limit the incoming or outgoing emails when using POP or IMAP.
However there is a limit of 8MB attachment size for our webmail clients. If you have a file larger than 8MB, that you need to have to send as an attachment via webmail you will need to either compress it with a popular compression program (such as WinZip), or break the file down into smaller units (if possible), otherwise we recommend using FTP (File Transfer Protocol) process or use a mail client such as Outlook or Outlook Express.