Skip to content

Import Outlook / Microsoft 365 mailboxes from a CSV

Microsoft stopped allowing a username and password to connect a mailbox over IMAP in 2023, so Microsoft 365 mailboxes can only be connected by signing in to Microsoft itself. This import does that sign-in for each mailbox in your file. It needs one extra thing the IMAP import does not: one row for a Microsoft administrator of each domain, because only an administrator can approve mail access for an organisation.

  1. Download the sample file

    Open Inboxes, select the arrow beside Connect inbox, then Import Outlook / M365 mailboxes, and download the sample CSV. It has two example rows on purpose: one administrator and one mailbox.

  2. Add one administrator row per domain

    For each email domain in your file, add a row for a Microsoft administrator of that domain and put TRUE in the is_admin column. That account is used once to approve the connection and is never added as an inbox, so it will not send anything. It must be a Global Administrator, Privileged Role Administrator, or Cloud Application Administrator — an Exchange or user administrator cannot approve applications. A domain that has already been approved does not need this row again. A Microsoft administrator almost always signs in as admin@yourtenant.onmicrosoft.com, which is not the domain your mailboxes are on. When that is the case, put the domain they approve in the domain column of their row — for example admin@contoso.onmicrosoft.com with contoso.com in domain. If one administrator looks after several of your domains, list them separated by commas in that one cell instead of repeating the row.

  3. Add the mailboxes

    One row per mailbox, with its email and password. Leave is_admin and domain empty on these rows — a mailbox already tells us its domain, and only the administrator row needs that column. First name, last name, daily limit and tags are optional. If an account asks for a code from an authenticator app, put that account’s setup key in totp_secret — without it we cannot answer the prompt and that mailbox is skipped.

  4. Upload and review

    Drop the file into the dialog. Before anything is uploaded you will see how many mailboxes were found, which domains they belong to, and whether each domain has what it needs. Any row we cannot read is listed so you can correct it. Fix anything flagged, then select Import.

  5. Read the results file

    Each mailbox is signed in one at a time, so a large file takes a while. When the run finishes you get a results file by email and from the progress panel. It repeats your original columns, without the passwords, and adds what happened to every row and what to change if it did not connect. The download link is available for 48 hours.