Asking for opinions of POP vs. IMAP vs. Exchange.

IMAP vs. POP vs Exchange (are there others than these?)

I think I know the basics -
exchange deals with contacts and calendar also (POP and IMAP don't).
POP takes emails off the server (OK, it could leave it on the server too) & sent messages stay only on the device
IMAP - is it wrong to call it the poor man's exchange?  

More of a real life situation - usually small businesses have shared hosting for their domain.  And limited space for storage as part of the shared hosting...

So while IMAP is 'better' than POP (since all the sent / received mail is in 1 place - on the server, regardless of the number of devices you use to check mail, keeping all your mail on a shared hosting plan for a bunch of employees can fill up your storage allotment?  Right?

JUst like to hear experts thoughts on why you like 1 over another (but don't think I need a lesson on the differences) / does 1 method not work realistically?

Does imap on a cell phone with lots of past emails / folders and keeping all that in sync burn up lots of data?
I know getting a new phone and getting sent items from a pop account is a pain.

Seems exchange is the 'optimal'? Is that safe to say?  you get big mailboxes (I am thinking office 365), contacts, calendar in sync across devices and between employees if you want.

But the cheapest way to get exchange?  $4 / month?  I heard is now using exchange? That's free and you get calendar and contacts? But yeah, an address.  Or is the exchange for a scaled down / handicapped / limited version vs. what you get / what you can do with regular office 365?

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JohnBusiness Consultant (Owner)Commented:
POP is used for 1 or 2 computers to keep mail on the computer (and left on the server for 2 weeks or so). I like it because, irrespective of suppliers that come and go, I have all my mail going back to 1996 on both computers.

POP offers built-in Calendar and Contacts that I sync with my iPhone.

IMAP is poor man's Exchange. It works. You can fill it up. And the supplier can vanish (has happened). The cons of IMAP outweigh any Pros.

Exchange is great if you can have it (Hosted Exchange is fine) because Calendars and Contacts can be managed and are better in Exchange.

In order of value:  Exchange (normally for business); then POP (for safety); then IMAP if you must.
nociSoftware EngineerCommented:
IMAP is not poor mans Exchange.... IMAP is a protocol for retrieving some IMAP servers also implement a mail database (Cyrus), others just take the storage that already exists (maildir f.e.) and exposes this to remote apps.  It's name says it all:  Internet Message Access Protocol
It is Equivalent to calling POP (Post Office Protocol)  poor mans exchange.. or SMTP (Simple Mail Transfer Protocol) poor mans  exchange.  

SMTP -> send mail between to & between MTA's (Mail Transfer Agents aka Mail servers).
POP -> used to fetch mail from a pigeon hole at an ISP, ISP's dont want huge mail stores from their users, so ideal for this (by default everything gets fetched...) then mail store is transient.
IMAP -> used to get mail from a more permanent mailstore. Ideal for mobile uses & central storage.
IMAP/POP are mostly implemented by MDA (Mail Delivery Agents)    where the Webbased & "regular" mail agents (MUA's) can access those.

Exchange is POP, + IMAP + Mail Store + Webbased Mail access tool + SMTP handler + X400 mail handler (now dead, but it started with it).,  Directory service (used to be X.500 ). + Calendar + MAPI ....

They are not even in the same class of object.

My Setup:
Exim (MTA) , rpsamd (Mail washer street), Roundcube (MUA, Webmail), Dovecot (MDA, for IMAP) the Mail store a a Maildir database.
Kmail  (MUA for KDE) but could be others as MUA... For calendaring & Contact store i user NextCloud. (Should also have a mail frontend but never used that part) a webbased cloud service.  All on a private server.

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just a few notes :

- IMAP works arguably much better than MAPI ( exchange protocol ) or activesync ( MAPI over HTTP with a bunch of hacks ) do : MAPI will more or less always sync everything. IMAP is much more versatile and is able to sync mailboxes independently, sync headers only, allow the same client to run concurrent sessions...

- POP is not something i'd even consider unless i'm on a satellite connection with 2s round trip time to the remote server.

regarding contact and calendar sync, there is no "better" technology ( though i can state the way exchange handles contacts is plain dumb... but it does arguably work ). i like caldav and carddav, but what's important is to be reasonably compatible with what other people use as well in your company.

as a general rule, it is nice to be able to provide multiple options to the users : i've been experimenting with sogo quite happily for mobile sync, while also providing caldav and regular imap, and even used hybrid setups having the email on imap, and the contacts and calendar synced over MAPI. ( note that many non-exchange products feature mapi and/or activesync nowadays )

one last note : it is perfectly feasible to sync calendar entries over plain IMAP ( and actually compatible with the way exchange stores them ). likewise for contacts but don't expect exchange compatibility unless you want to resync the whole folder every time there is a modification.

the choice is very dependent on what you actually need, and what your clients are used to work with : for example contacts syncing is useless to many people in offices because they'll use an ldap address book for pretty much everything and maybe your own clients all have iphones so their personal contacts is already synced with icloud anyway...
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INeedYourHelp00Author Commented:
thanks everyone!  First, most of the terms you guys mention go WAY over my head.  I've heard of caldav, never heard of most of the things you mention noci <g>

some clarifications - calling imap as 'poor mans exchange', what I think I meant is that you get it free as part of web hosting plans 9the poor man part of my cliche) and keeps emails (only) in sync across all your devices - delete it once and it's gone. (the exchange part of my cliche).

But yes, you lose contact and calendar sync.

Skulll: you say

many non-exchange products feature mapi and/or activesync nowadays

Again, I guess I don't know what else is out there.  

I'm coming from a windows / business background where exchange, pop and imap are pretty much the options. But again, as Noci describing his set up, whoosh!  over my head.
Jeff GloverSr. Systems AdministratorCommented:
Everyone has their own opinions on this but one thing bothers me about your original question. It is Apples and Oranges. POP and IMAP are protocols where Exchange is a Server providing comprehensive Messaging services (how comprehensive depends on your point of view of course).  Exchange supports POP and IMAP but also gives you MAPI or  RPC over HTTPS connecitvity to mail via a full features client like Outlook.
  POP clients download mail to the device but can be told to leave a copy in the server
  IMAP downloads the headers only and retrieves a copy when you select the message.
Outlook can either keep a copy locally (Caching, it is the default) or not. Your call.
  For "" and Office 365, yes, they are using Exchange for the Mail back Ends. After reading your full question, I think you are missing the point a little. You are looking at things from the client side. You can connect to Office 365 with a POP client, an IMAP client, a Web Browser, or with a Full featured client like Outlook. As others have said, it really is what you want.
  As far as cost, yes for a single mailbox, the basic Office 365 subscription is pretty cheap but once you get into enterprise level numbers, it can be cheaper to have your own on premise exchange environment.
JohnBusiness Consultant (Owner)Commented:
calling imap as 'poor mans exchange', what I think I meant is that you get it free as part of web hosting plans 9the poor man part of my cliche) and keeps emails (only) in sync across all your devices -

Perhaps "poor man's Exchange" is the wrong term. and IMAP can allow several devices to look at the mail. My old Blackberry and my newer iPhones use IMAP to leave the mail.

Then I use POP email (for my own sanity and security) to keep mail on two computers and then I delete it later.
Again, I guess I don't know what else is out there.  

sogo and horde both work reasonably well


it might help to know what you actually need first and what kind of knowledge your admins have so we can point out one or several good fits.


regarding terminology in this thread :
protocols ( POP, IMAP, MAPI, activesync ) are the language the programs speak.
Mail Transfer Agents ( exim, postfix, qmail, sendmail... ) can transfer mail to the destination
Mail User Agents : ( outlook, thunderbird, kmail ...) no need to explain i figure
Mail Servers ( dovecot, courrier, ... ) provide POP/IMAP/... services ( all provide an Local Delivery Agent which is the hook they expose to the local MTA )
Webmails : roundcube, horde, ... sometimes provide activesync as well

exchange combines most of the above features
sogo is a kind of middleware/server mix which provides exchange-like features over MAPI/activesync. it relies on a different mail server to store the mail and can use various vackends for calendar and contacts

hope that clarifies
nociSoftware EngineerCommented:
Other functional replacements: OpenExchange, Kolab,  (complete mailsystems)

Additional with the development of cloud systems, also personal clouds started (ones you can run On-premises instead of somewhere...
There are a few with quite a lot of features: like NextCloud, Owncloud,
They offer interfaces to mobile equipment  File access (Webdav), contact access (CardDav), calendar access(CalDav) together with a web frontend. For file storage, contact management, calendar management.
They don't do mail, but have some frontend to access IMAP based services.

Bottom line is we can mention a lot of solutions... to a lot of problems..., but what exactly is your challenge here.
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