Weighing in again as the person who started this :-)
Kostya, I think (not sure though), that right now the alias on Office365 works only on the web for Outlook.com, not through the mobile clients. That _might_ be why it didn't work with Aquamail.
Coming back to Exchange. Quite a lot of stuff has recently happened for exchange in Aquamail, and supporting distribution lists etc would be a logical step. As mentioned by dennosius above, it would also be the only android exchange client with this feature.
Since there was a question mark about the Distribution List, taking a short detour. A DL is basically a mailing list. Eg an id called alias@xyz.com with 3 members. Any mail addressed to alias@xyz.com is automatically forwarded to the 3 members - there is no mailbox called alias@xyz.com. Related concepts are Shared mailbox (which keeps the mail in a separate mailbox called alias@xyz.com which the 3 members can access), and Groups (which again keeps the mail in alias@xyz.com, but also add a sharepoint site, planner, calendar etc). DLs are (for now) the lightest, and also don't need a separate mailbox to be setup or accessed by the client.
The original request was for O365 for business (eg contoso.com, closer to exchange), and not O365 consumer (eg outlook.com, closer to internet mail).
Actually, the process for O365 (business) is not that different from Gmail or other internet mail
1. Set up alias account to send from : Internet: set up account. Exchange: Set up DL
2. Give Send As permissions: Required in both
3. Decide whether to ask for which account to send from or to send from the recieving account: Required for both.
The only real difference is that in internet mail, most people would do it themselves as admin, while in Office 365 (corporate), the corporate admin might be required.
Would be great if, as requested in the post above, there could be a test apk, which has 2 features for Exchange accounts (like the identities for IMAP).
1. Add alias names (or more accurately, DL names)
2. Replace the From in the outgoing mail with the email id of the incoming mail when coming through a DL.
All the server side setup would be done by the testers.
To avoid confusion,
1. Instead of identities, we can call them DLs or Groups?
2. Maybe like Gmail and Office 365 accounts, there could be a category called O365 for Business
At least we can test the concept. If it does work, it would be really useful for work emails, and the communication / support can be thought through before sending it to production.