On android 13 running version TQ1A.221205.011.2022120700 of GrapheneOS I am seeing this situation:
I have email address email1@msn.com – An Outlook email address requiring Oauth2 – and I have a rule set up that all emails received at email1@msn.com are kept in the inbox there but are also immediately forwarded to the inbox at email address email2@dismail.de .
On my android device K9 version 6.400 from F-Droid is set up using OAuth2 for email1@msn.com, and the Fair email app is set up for email2@dismail.de . In K9 the inbox folder is a class 1 folder, and I have these settings:
Sync messages from: any time (no limit)
Fetch messages up to: 2 MiB
Folder poll frequency: Every 15 minutes
Poll folders: 1st and 2nd Class folders
Push folder: Only 1st Class folders
Here is what is happening, I will use a recent email sent to me as a very typical example:
A person sent an email to me, sending it directly to email1@msn.com , no other email addresses were included in the distribution of this email. The email was a short paragraph of text only, no attachment. Within one or two minutes of this email having been sent it appeared on my android device in the forwarded to email address of email2@dismail.de visible in the Fair email application. The email did also eventually appear in the direct recipient email address of email1@msn.com in the K9 application on the same android device, but roughly six hours (!) later. I am seeing this kind of situation happen many times with emails sent to email1@msn.com . I never see emails sent to email1@msn.com show up in K9 more timely than 15 minutes later, but many times there is a much longer delay.
Question: Why would it take between 15 minutes and several hours – but never more timely than 15 minutes - for an email to email1@msn.com to be received by the K9 application?