Yes. Outlook for iOS and Android supports a maximum of 25 accounts. For mail accounts that aren't synced to the Microsoft Cloud (for example, some Gmail, Yahoo, iCloud, or IMAP accounts), you can add up to 15. There's no separate limit on storage accounts, such as OneDrive and Box. These limits help keep Outlook running smoothly for everyone.
For more information, see Sync your account in Outlook to the Microsoft Cloud and Outlook for iOS and Android in Exchange Online: FAQ.