How is sender identity chosen / controlled?

[aussieboykie]

Under Composing and Sending my default account is set as me@my.domain and this works as expected most  of the time. My domain is managed by FastMail and I never want to use my underlying FastMail address; every email should come from me@my.domain. Yesterday, in AquaMail on an Android tablet I replied to an incoming email and noticed that my FastMail ID was populated into the sender address field. As a test, I tried replying to another email from a different sender and me@my.domain was correctly populated into the sender address field. Further tests show that when I reply to any email from this particular sender, my FastMail ID is chosen.

Any ideas? I don't see any way of configuring special treatment for a specific identity. There is nothing obviously special or unusual about the sender's ID. It is a HotMail address.

[Kostya Vasilyev]

It checks the list of recipients in CC / BCC to see if these include the address of any of the configured aliases (in the account in which the message was received).

[aussieboykie]

The incoming email is addressed to me@mydomain.com and there are no other addressees in To:, CC:, or BCC:. 90% of all emails I receive are addressed the same way and to date it is only when replying to this specific individual that the issue occurs. A more concerning aspect of the problem is that my reply is not saved in FastMail's Sent folder and yes, the sender does receive my response. Is there a log I can check or a debug option I can activate to see what is going on?

[Kostya Vasilyev]

Re: it is only when replying to this specific individual that the issue occurs

Well do you see if there is anything special about messages from this individual? In the headers?

Re: my reply is not saved in FastMail's Sent folder

Only messages sent to this individual or all of them?

Please check that the app's "Sent" folder is "mapped" to the right folder on the server:

- Long press on the account on the app's main screen
- Options and folders -> Folders
- Wait 10-30 seconds for the app to refresh the folder list

- Find "the" Deleted folder ("Deleted Messages", just "Deleted", "Trash", "Bin"... can vary.. for Gmail it would be under "[Gmail]" or "[GoogleMail]")
- Tap its name, choose "Sync as Deleted".

- Same with Sent and Drafts ("Sync as Sent" / "Sync as Drafts")

PS - yes there is a debug log capability, please see a link in my signature just below.