4) 'An operation on the server timed out. The server may be down, overloaded, or there may be too much net traffic. Mail could not be sent. Account name: 'Dot Mac Account' Most likely the server just timed out. This could be a problematic message causing the error, or it may be that your ISP is blocking TCP traffic on port 25 (the SMTP port).
We are in the process of migrating users from iMAP server with Rackspace to Exchange. It is a Hybrid environment as some users will be staying with the iMAP service (legal reasons).
How the issue is we have migrated most of our users over and configured their accounts in outlook but they keep complaining that their messages arrive on their phones much faster then in the 2016 Outlook for Mac. It if was a few seconds we would not have a problem but sometimes it is 10 minutes before the email appears in Outlook even with multiple 'send receive' attempts. The mailboxes range in size from having a few hundred emails to some of the larger accounts having 20k - 30k emails in the one account. Rackspace at this point is being not help.
Title Start Date & Time End Date & Time Friday, December 21, 2018 - 10:00pm Friday, December 21, 2018 - 11:59pm Thursday, December 27, 2018 - 5:00am Thursday, December 27, 2018 - 7:30am Friday, January 4, 2019 - 4:00am Friday, January 4, 2019 - 7:00am Wednesday, December 19, 2018 - 12:01am Monday, January 7, 2019 - 11:59pm Tuesday, January 8, 2019 - 6:00am Tuesday, January 8, 2019 - 7:00am Wednesday, January 9, 2019 - 5:30am Wednesday, January 9, 2019 - 6:45am Monday, November 26, 2018 - 6:00pm Wednesday, January 23, 2019 - 10:00pm.