I uploaded a mailbox file and the rows went red. What does each reason mean?

After an upload, Monty signs in to every inbox and shows one line per row. Green means it works. Red means it could not sign in, and the line says why. Here is what each reason means and what to change. Whatever the fix, re-uploading the same file updates the rows in place — nothing is duplicated and no extra mailbox slots are used.

1. 1“Could not reach the IMAP server at …” or “… the SMTP server at …” — the server name or port in your file is wrong, or is a template placeholder such as imap.example.com. Google inboxes need no server columns at all; delete them and Monty fills in the real ones. For any other provider, copy the IMAP and SMTP server names from their settings page.
2. 2“Google rejected the sign-in” — the password in the file is the account password, or an app password that has been revoked, or 2-Step Verification is off for that account. Generate a fresh app password (linked below) and put it in the file.
3. 3“Google only accepts a 16-letter app password here” — shown in the preview before anything is imported. The password column holds something that is not an app password. Same fix.
4. 4“The server refused IMAP” — IMAP is switched off for that account. A Google Workspace admin turns it on under Apps → Google Workspace → Gmail → End User Access → Enable IMAP for all users. For bought inboxes, the admin is the provider.
5. 5“… is on Microsoft 365” — Microsoft no longer accepts passwords from tools like Monty. Close the upload and use Connect → Microsoft for each inbox, or Connect your whole team for one admin approval.
6. 6“Your plan allows N mailboxes and this workspace has N” — the plan's mailbox count is full. A mailbox that could not sign in still holds its slot until you remove it; delete the red ones from the list and upload again, or add mailbox slots in Billing.
7. 7“The server did not answer in time” — try the upload again in a minute. If the same rows time out twice, the server name is probably wrong.

Download failed rows gives you a small file of just the addresses that need fixing, with the reason beside each. Fix those in your provider's file, then upload only the fixed rows.