On year 2020, the release at playstore is from 2018. Of course there is no problem. The email protocols they dont have something new. https://play.google.com/store/apps/details?id=com.fsck.k9
there are pre-releases up to date at https://github.com/k9mail/k-9
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I would like to explain IMAP Push. When setup an IMAP account by default the
Account > Settings > Fetching mail > Push folder
is activated.
This option is only available for IMAP accounts. When it is enabled a long-lived connection to the IMAP server is established so K-9 Mail can be notified by the server when a new message has arrived. When this is set, you do not need to select a poll frequency, because you do not poll. src
You can disable this by setting the Push folders to none. Then you have to set the
Account > Settings > Fetching mail > Folder poll frequency
example to every hour.
but seems that this occurring
K9 No Longer Auto Syncs
https://github.com/k9mail/k-9/issues/3167
IMAP Push
It should reduce the time and effort needed to synchronize messages between the two by using an open connection that is kept alive by some kind of heartbeat. To reduce necessary bandwidth, it uses compression and command macros. Additionally, P-IMAP features a mechanism for sending email that is derived from (but not identical to) SMTP, and so a rich email service is provided using a single connection. src
?? most mobile email apps don’t support IMAP IDLE (push) because of the battery hit that it causes.
I have used K-9 in the past but moved to AquaMail (not open source) more recently which does IMAP-IDLE/push as well.
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