When "Push" is configured, emails arriving into the Microsoft Exchange inbox are instantly pushed to the device.
Calendar events sync both ways between Exchange and the device.
Yahoo Mail may be pushed to an Android device, as Android now supports IMAP4 (as of September 2015).
The Nokia asha smartphones and select models of Nseries smartphones and newer s60 and Symbian^3 handsets running symbian os 9.x or Symbian^3 support the Mail for Exchange software, which is compatible with Microsoft Exchange Server Active Sync and Direct Push, allowing the Nokia smartphones to receive push email as well as sync contact lists, calendars, and tasks with Exchange servers.
Global Address Lookup is also supported, starting with version 2 of the Mail for Exchange software.
'Direct Push' technology is an additional feature added to Microsoft Exchange 2003 with service pack 2 that adds messaging and security features.
A phone device running Windows Mobile 5 is enabled to poll the Exchange Server every 30 minutes.
Numerous Yahoo users have complained that push does not function reliably; Yahoo has attributed this to server issues rather than the Smartphone app.
In 2010 Hotmail, and its replacement, Outlook.com, have been made push configurable for Android smartphones through the default mail application.
Outgoing mail is generally pushed from the sender to the final mail delivery agent (and possibly via intermediate mail servers) using Simple Mail Transfer Protocol.
If the receiver uses a polling email delivery protocol, the final step from the last mail delivery agent to the client is done using a poll.
For example, a user with a laptop on a Wi-Fi connection may be assigned different addresses from the network DHCP server periodically and have no persistent network name.
When new mail arrives to the mail server, it does not know what address the client is currently assigned.
To achieve push mail with email providers other than Exchange, there is a commercially available plug-in from Emansio that enables push mail with almost any public email provider, or any email server that supports IMAP IDLE.