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Can you help me with my capacity planning?

As the title sugest i would like your feedback about IMAP accounts, any sugestion experience you have with it would be apreciated... My current goal is migrating a mail server that is using pop to imap. The server should handle about 1000 mail accounts so i would like to ear your opinion about bandwidth, machine required power, your personal experience with this protocol, etc... Thanks in advance


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marked as duplicate by Sven, Ward, voretaq7 Jul 28 '12 at 4:13

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

All the key factors in sizing an email server relate to volume. The fact that you're using IMAP means that you'll have a server-side storage need that differs greatly from POP3 but, beyond that, there's really not much about the protocol that radically changes the server's performance.

You need to know about the incoming / outgoing message counts and average sizes and the caching behavior of client software you can't size bandwidth.

You need to know about the number of items users will be storing persistently and their retrieval frequency (and, again, the caching behavior of client software) you can't size for storage or I/O performance.


My experience has been that IMAP puts orders of magnitude more load on a server than POP.

POP basically gives all the emails a number you asked to retrieve or delete a message based on it's number, not much going on. IMAP on the other hand is a much more complex protocol, most significantly clients can perform server side searches of their mail.

It's not the number of mailboxes that will be the issue but the size of the mailboxes. Once you have accounts with over a few hundred MB you are going to need a powerful server. it's CPU and RAM that will be the issue, even with 1000 users bandwidth will unlikely be a concern 10Mb would be fine.


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