Background: this is because of the introduction of [doze mode](https://developer.android.com/training/monitoring-device-state/doze-standby) in Android 6 Marshmallow.
If this doesn't work, see here for more solutions: [https://support.google.com/mail/accounts/answer/78754](https://support.google.com/mail/accounts/answer/78754)
See here for more information: [https://support.office.com/en-us/article/what-is-a-microsoft-exchange-account-47f000aa-c2bf-48ac-9bc2-83e5c6036793](https://support.office.com/en-us/article/what-is-a-microsoft-exchange-account-47f000aa-c2bf-48ac-9bc2-83e5c6036793)
The error message *UIDPLUS not supported* means that your email provider does not provide the IMAP [UIDPLUS extension](https://tools.ietf.org/html/rfc4315).
This IMAP extension is required to implement two way synchronization, which is not an optional feature.
So, unless your provider can enable this extension, you cannot use FairEmail for this provider.
All well known IMAP servers support IMAP with a plain SSL connection, so there is no need to support STARTTLS for IMAP.
If you encounter an IMAP server that requires STARTTLS, please let me know.
For more background information, please see [this article](https://www.eff.org/nl/deeplinks/2018/06/announcing-starttls-everywhere-securing-hop-hop-email-delivery).
tl;dr; "*Additionally, even if you configure STARTTLS perfectly and use a valid certificate, there’s still no guarantee your communication will be encrypted.*"
* Preview message text: this is not always possible because the message text is initially not downloaded for large messages and besides that the subject is supposed to tell what the message is about.
* Filter rules: filter rules should be executed on the server because a battery powered device with possibly an unstable internet connection is not suitable for executing filter rules.
On some devices, where there are lots of applications competing for memory, Android may stop the synchronization service as a last resort.
Some Android versions,
in particular of Huawei (see [here](https://www.forbes.com/sites/bensin/2016/07/04/push-notifications-not-coming-through-to-your-huawei-phone-heres-how-to-fix-it/) for a fix)
or Xiaomi (see [here](https://www.forbes.com/sites/bensin/2016/11/17/how-to-fix-push-notifications-on-xiaomis-miui-8-for-real/) for a fix)
**(23) Why do I get 'Too many simultaneous connections' ?**
The message *Too many simultaneous connections* is sent by the email server when there are too many connections to the same email account at the same time.
Possible causes are:
* There are multiple email clients connected to the same account
* The same email client is connected multiple times to the same account
* The previous connection was terminated abruptly for example by losing internet connectivity
**(25) Why can't I select an image, attachment or a file to export/import?**
If a menu item to select a file is disabled (dimmed),
likely the [storage access framework](https://developer.android.com/guide/topics/providers/document-provider),
a standard Android component, is not present,
for example because your custom ROM does not include it or because it was removed.
FairEmail does not request storage permissions, so this framework is required to select files and folders.
No app, except maybe file managers, targetting Android 4.4 KitKat or later should ask for storage permissions because it would allow access to *all* files.
If you have another question, want to request a feature or report a bug, you can use [this forum](https://forum.xda-developers.com/android/apps-games/source-email-t3824168).
