IPhone 6 very long delay before receiving messages

Delta Chat version
Currwnt

Expected behavior

Send message to Jane
Jane receive message notification with 15 minutes

Actual behavior

6 hours to 3 days elapse prior to notification

Steps to reproduce the problem

Have a mailo.com account as the Jane

Screen snapshots

Debug logs

Logs
<!--
If applicable, debug logs can be copied from within the Delta Chat app: 

Open the _Settings_ menu -> _About_ -> _version number|Info_.

Alternatively from the Android system log:

` adb logcat -v time -s DeltaChat `

This log contains private data (e.g. mail address, provider information) which shall be removed or anonymised prior to posting.
-->