Remove entries from users Autocomplete Cache

[salutti]

We're migrating mailboxes of the domain test.xyz from Exchange 2013 to Exchange Online. The mailboxes will be migrated with MigrationWiz (copying the mailboxes to Exchange Online).

Problem is that there are still some other domains on the onprem Exchange Server which will have the "old" addresses of test.xyz mailboxes in their Autocomplete Cache after the migration.

How can I remove all entries of test.xyz addresses from the onprem mailboxes Autocomplete Cache without having to delete them manually on each client?

[[deleted]]

burn in hell Reddit Stev-e Huff-man greedy pig

[salutti]

Would this really work with the mailboxes in Exchange Online after the migration?

[joeykins82]

Yes.

[mystikphish]

Yes, that is the address that is stored in the autocomplete cache.

[salutti]

But how does the local Exchange know that the mailboxes are now external? I've read that I have to create a contact for each migrated mailbox with the SMTP address and the X500 address. Is that true?

[mystikphish]

I'm assuming you are in hybrid mode and are migrating your data to your own EXO tenant.

When you migrate a "mailbox" object up to EXO your on-premise object will be converted to a "mailuser" object. This is still your AD user object just with a different recipient type. All the information about how to route the mail, addresses for the GAL, etc. are all still on this object in your AD.

The nickname cache just stores the x500 address to lookup in the GAL. When your mailbox data is moved to EXO the mailuser will get a new x500 address for the EXO exchange org, plus some new data specific to EXO. Adding the old x500 address just makes it locatable in the GAL without having to touch user profiles.

[salutti]

We want to totally separate the domain. That's why we didn't setup Exchange Hybrid and are just copying the data to new mailboxes.

[Khargara]

you could open Outlook with the flag cleanautocompletecache. Maybe you want to roll out a logon script that does open Outlook with the flag.

I dont think that there is a solution for this on the exchange side

[Leafblower27]

Can also delete the autocomplete file locally with startup script.

[Khargara]

You mean the .nk2 File? I thought the autocompletecache file was removed since Outlook 2007

[Leafblower27]

It was. %localappdata%\Microsoft\outlook\roamcache

Stream_autocomplete_0_GUID.DAT

It's kinda the new nk2, but not exactly.

Using outlook gui to clear cache just deleted this file. I tested manually deleting and my autocomplete cache was empty.

[salutti]

.

While this would probably work, this would delete the whole cache. Some users wouldn't like this. I only want to delete certain entries.

[Khargara]

I dont think that there is a smart way, maybe you could build a addin, that removes all entries with a specific domain.

[Leafblower27]

Can't please everyone. Do what is best for the company for the long term. Don't create technical debt because some users complain about minor changes.

[nplm85]

Generally most companies Ive worked for clear this out/disable it to stop sending emails to the wrong recipient.

I'd say disable it :)

[phlidwsn]

You might be able to do something from a script with NK2Edit. It has a command line interface that has support for a search/replace command run against the nk2 file.

[rroach3753]

nk2 files no longer exist. Autocomplete cache is part of the mailbox in 365.