[camner]

Originally Posted by jhollington

From what you describe, I can't see any reason why this shouldn't be working properly, so I'm probably missing something here in either your configuration or how you're doing things

Or, more likely, I just didn't make myself clear!

To be clear, when you say "I have FM options set so that any email that gets sent through the FM SMTP server has a copy put in the Sent folder." are you sure you've checked off the Save a copy when sending through 3rd party email clients?

Correct...I have checked off the Save a copy when sending through 3rd party email clients box.

If you're using multiple identities, you'll also need to make sure that you've enabled this option on all of the identities where you want this to happen — in particular whichever identify is the one you have configured in your iOS Mail settings.

Yes, though this seems to be happening by default. I just recently set up several new identities and I did NOT manually check that box! Perhaps that's the default action?

You say you're using the FastMail app, so I assume that normally you send mail from your iDevices solely through the FastMail app, except when you're using things like built-in sharing tools, correct?

Yes

I'm guessing messages sent through the FastMail app are landing correctly in your "Sent" folder?

Yes

How have you configured your account in your Mail settings on iOS? There actually isn't a setting on the iOS side to not save messages in your Sent Items folder, so at that point I'm assuming that you're either not using an IMAP account or you've configured your "Sent Mailbox" to be a folder on your iPhone/iPad or your Trash folder (in which case you're still technically getting a duplicate — it's just ending up saved locally only or landing in your IMAP trash folder).

You are correct. I have configured the "Sent Mailbox" to be a folder on the iPhone/iPad.

IMHO, the "easier" approach is probably just to NOT use the Save a copy when sending through 3rd party email clients setting and let IMAP do its thing from your iDevices and other IMAP clients. It will push the message into your "Sent Items" folder after sending, and the FastMail app on your iDevices will pretty much do the same when sending from there.

I agree that this seems to be an easier approach. I think the issue for me is that I don't really know how to tell iOS which mail account to use when using the sharing tools. I have several accounts set up in Mail; how does iOS determine which one to use when sending email via the sharing tools?

Also, since outgoing mail is handled by an SMTP server, (1) how does iOS determine which to use when using sharing tools, and (2) since SMTP doesn't have anything to do with IMAP (AFAIK), how exactly would "let IMAP do its thing" actually result in a copy of the email ending up in the Sent folder of Fastmail?

Thanks very much for your extensive reply. Despite your great explanation, I'm still a bit unclear about a couple of things...