You should be able to copy your messages from outlook data file to IMAP server.
I've done it many times, but mostly data file -> Exchange Server.
First of all think about do you really need to transfer old email to a new server. You can delete your old account and simply open the data file in Outlook to have an archive of the old emails. If you need them to sync to another device, then keep reading.
First you need to locate the data file that contains your old messages. You can do so by going into account setup and there will be a tab called data files. In there you can figure out which data file is the one that holds old mail. There should be a button to open file location.
Next copy it in a safe place so you can open it in case you mess something up (you have to close Outlook first).
Then you can delete the old account so it stops bugging you while you keep working form account settings.
Your old mail should remain open after you delete the account, but if it goes away you can do File -> Open outlook data file (or File -> Import for older versions and follow the wizard).
If your IMAP account is not setup, do so now.
You should now have two email accounts and you can drag and drop mail between them.
Some advice:
- Backup your IMAP mail before you begin.
- I suggest you create a folder for your old mail on the IMAP server, something like "archive", you can move it to Inbox later if you wish
- Do not under any circumstances copy all of your messages at once! It will crash and burn!
- Locate your oldest message in old mail and create search folder to filter messages starting from the oldest date for the next week or month, depending on how many messages you have. Never go more than 500 at a time with 6GB RAM, but if you have attachments bigger than 5MB, go even less - say 300
- Write down how many emails there are in the search folder
- Copy messages from the search folder to your IMAP folder
- When it's done check how many messages are there in your IMAP folder and see if it matches what you have in the search folder
- Modify the search folder for the next date range (say if it was 1.Jan 2013 - 15.Jan 2013 move it to 16. Jan 2013 - 1. Feb 2013.)
- Take a note how many emails are in your new date range
- Copy them to IMAP server and check how many are there, it should be the SUM of numbers you have written down
- If it matches repeat, if not you can create search folder for your IMAP account to narrow down where the problem was. Some messages are stubborn and will have to be copied individually
That is about everything I can think of right now, but if you run into a problem let me know, and I'll see what can I do to help.
You will probably have some problems, this never ever, ever goes smoothly but it's the simplest way to get it done.
Can you check if old mail is in Outlook data file? If so you can copy it to the server via Outlook. – Enis P. Aginić – 2014-12-02T14:23:44.920
The old mail has always been received through Outlook, so I suppose it is. I do not have direct access to their computer as it's a 45 minute drive. However, if I do this through Outlook, how would I do this without getting the constant warnings that the old login doesn't work anymore? I can't move any of their mail with these warnings. – Ruben Rutten – 2014-12-02T14:28:41.853
1Yes, you can open data file without setting up the account then copy and paste mail into the new one that is connected to the IMAP server. There are some pitfalls but I will explain when i get to a PC, can't type that much on a phone. – Enis P. Aginić – 2014-12-02T14:40:42.110
I'll await your reply. Do you have any indication on how long it will take? – Ruben Rutten – 2014-12-02T14:54:08.050
How long it will take is a question impossible to answer. If there are 100,000 messages that are essentially plain text it might not take as long as 100 messages with 50meg attachments. Also unknown is the upstream bandwidth at your customers location. – Tyson – 2014-12-02T14:57:33.720
I meant how long it will take before he has access to a PC. – Ruben Rutten – 2014-12-02T14:58:04.967
I'm not sure what he has in mind for pitfalls, my advice tho is to take it slow, don't try to copy the entire contents at one time. Plan in advance smaller chunks to copy and paste from folder to folder, it will be easier to recover from errors. be sure to use COPY and not MOVE, while move seems more logical I've created larger messes to resolve using MOVE over COPY. – Tyson – 2014-12-02T15:04:02.547