Overview of EAS vs. EWS vs. IMAP vs. MAPI

There is some confusion over the various types of synchronization options that are available for desktop and mobile email clients and devices. To clear some of this up let's first look at each protocol.

Applies to All Versions of SmarterMail

Exchange Web Services (EWS) - A protocol introduced by Microsoft for Exchange that was intended for desktop email clients such as Microsoft Outlook. EWS was intended to be Microsoft's replacement for the legacy MAPI protocol. At this time, Microsoft Outlook 2015 for Mac from Microsoft 365 (Office), Outlook 2011 for Mac, Apple Mail, the Outlook client for iPad, and eM Client all support EWS. 

Exchange ActiveSync (EAS) - Another Microsoft protocol developed for use on mobile devices such as phones and tablets. EAS is also available for use with Windows 8 Mail, People and Calendar.

IMAP - One of the most pervasive protocols for email retrieval, alongside POP3. IMAP is cross-platform and can be used by desktops and mobile devices. IMAP is extremely stable and reliable and is a perfectly acceptable way to synchronize your email across all devices.

MAPI - A Microsoft protocol that, in addition to other things, powers Microsoft Outlook's interaction with Exchange. Used solely with desktop clients, it provides a set of interfaces, functions, and other data types to facilitate the development of messaging applications. MAPI is what drives Outlook's ability to manipulate email data, create email messages and folders to store those messages, and supports notifications of changes to existing MAPI-related data. Currently, only Outlook utilizes the MAPI protocol.

So, what protocol should I use based on my mailbox size?

For your desktop, if you have a large mailbox, OVER 5,000 messages or 5GB of space used, MAPI is the ideal protocol to use as it works with email, calendars, contacts, tasks and notes. (Really, MAPI is the best protocol overall as it offers the most Exchange-like experience when using SmarterMail.) If MAPI is not available, IMAP is the protocol you should use for your email as it offers push-like support with the IMAP IDLE process, which pushes new messages to your desktop client at a set interval. For your calendars or contacts you can use any other of the sync protocols, such as CalDAV and CardDAV. IMAP 

If you are on a mobile device, EAS can be used, even with large mailboxes. The reason it works well on mobile devices, but not desktop clients like Outlook 2013 for Windows, is because mobile clients only ask for a set timeframe for synchronization, like a month of mail or less. It will not pull back all mail in your mailbox unlike Microsoft Outlook 2013 for Windows.

If you're on MacOS, EWS is the best protocol to use as it offers much of the same functionality as MAPI. EWS is also supported by other email clients such as eM Client. 

When I set up an account in Windows 8 Mail does it use EAS?

Yes, if you choose the "Outlook.com" option when setting up your account, Windows 8 Mail uses EAS by default and so it also syncs People and Calendar. Again, please see the guidelines above for which protocol to use when synching your desktop client to your mailbox.

If I don't have the EAS add-on for SmarterMail what do I do for my mobile devices?

Ideally, EAS is the best protocol for sycning mobile devices as EAS is designed expressly for that purpose. If it's not available, you may want to use IMAP for your email and CalDav and CardDAV to bring down calendars and contacts, respectively. This would all work with an Enterprise Edition of SmarterMail.

For more information, please refer to the SmarterMail Online Help.


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