The Mail app on iPhone can put an alias in the From line of a message, so the person you are writing to never sees your real address. iOS does not make the setup obvious, and Apple has moved the screens between versions, so half the guides you find describe menus that no longer exist.
Two different jobs get confused here. Answering a message that reached you through a forwarding alias, and starting a fresh conversation as that alias. Only the second needs anything configuring, and the first is the one most people are actually trying to do.
This guide covers the second job on an iPhone: what to have ready, the path through Settings as Apple's own documentation writes it today, and what to check when a send fails.
Start here, because you may not need any of this
If a forwarding service delivers mail to the inbox you read on your phone, replying to that mail needs nothing configured at all. A service that rewrites the reply path has already done the work. The copy that reaches you carries a reply address belonging to the service, so tapping Reply sends your answer back through it, and the service relays it on with the alias as the visible sender. No hostname, no port, no password, and replying without revealing your address walks through the mechanics.
One exception, and it deserves a paragraph of its own. Reply All. Only the sender's address was rewritten on the way in. The other people on the thread sit in your mail app as ordinary addresses, so a Reply All goes out to them from your real account and shows your real address on the way. On a thread where the masking matters, reply to the sender alone.
Everything below is for one case only: writing first, to somebody who has never written to you. If you never do that from an alias, you can stop reading here.
What to have ready
Your provider publishes all of these. Have them in front of you before you open Settings; iOS gives poor feedback when a field is wrong.
- The outgoing hostname your provider gives you. Not your main mail provider's server, and not iCloud's.
- The port. 587 is the submission port, reserved for exactly that by RFC 6409, and it pairs with STARTTLS. Port 465 with implicit TLS is the usual alternative.
- The username the provider issued for this alias. Often the full alias address, sometimes a separate account name.
- The password the provider issued for this alias, usually generated in its dashboard, not the password you sign in to its website with.
- Whatever the provider publishes for the incoming side, because iOS will ask for an incoming server too, and there is no send-only account on an iPhone.
That last line is the iPhone-specific catch. More on it below.
The walkthrough, from Settings rather than Mail
On iPhone you add mail accounts from the Settings app, not from within Mail. Apple's current instructions put the path at Settings, then Apps, then Mail, then Mail Accounts, then Add Account. The Apps layer is recent; older versions of iOS put Mail directly on the main Settings list, so screenshots from a couple of years ago no longer match. When in doubt, follow Apple's current page rather than a forum thread.
From Add Account, Apple's steps for a provider that is not in its list run like this. Enter your email address and tap Next. Tap Add Other Account, then tap Mail Account. Enter your name, the alias address, the password and a description, then tap Next. Mail will try to find the settings on its own, and if it succeeds you tap Done and you are finished.
It usually will not succeed for an alias provider, and that is fine. Tap Next, choose IMAP or POP as your provider directs, and enter the details for Incoming Mail Server and Outgoing Mail Server by hand: the hostname, the per-alias username and the per-alias password in each. Tap Next, and if the settings check out, tap Save.
Now the catch. iOS builds accounts around a mailbox, so the form requires incoming server details even when sending is all you want, and plenty of forwarding services have no mailbox to offer because forwarding is the whole product. If your provider publishes IMAP or POP details, use them. If it publishes nothing for the incoming side, the account cannot be completed, and the provider's own compose window is the shorter road. The same wall exists in Gmail and in Outlook, each for its own reasons.
Choosing the From address when you compose
Once the account is saved, Mail treats the alias as one of your sending identities. In a new message, tap the Cc/Bcc, From field to expand it, tap the From field, then choose the account. That choice applies to that message only.
Glance at the From line before every send; Mail fills it with a default, and the default is not always the address you meant. Then send a test message to an address you control and read it at the other end. The From line should show the alias, and nothing else in the message should mention your real account.
How this differs from Hide My Email on the same phone
Your iPhone may already have a second way to do this, and for some jobs it is the better one. With an iCloud+ subscription, Hide My Email generates unique, random addresses that forward to your personal email account, and it can send as those addresses from inside Mail with no SMTP settings at all: in a new message, tap the From field, tap it again, then tap Hide My Email. One published limit matters: a message sent this way can go to a single recipient only.
The honest comparison runs like this. Hide My Email costs nothing beyond iCloud+ and involves none of the setup above, but the sending happens inside Apple's own mail, so it works in Apple's apps and nowhere else, and the addresses live on Apple's domain rather than one you control. An alias on a domain you own moves with you when you change providers. If all you want is a few masks for newsletters and shop signups, and you already pay for iCloud+, use Hide My Email and skip the rest of this guide. The desktop half of the same trade-off is covered in the Apple Mail guide for Mac.
Troubleshooting
Authentication failures. Almost always one of three things: the username is in the wrong form, you entered the password you use on the provider's website where a generated per-alias password was required, or a stray character crept in while typing on glass. Go back to the account in Settings and re-enter the outgoing server credentials rather than assume they saved.
Ports and TLS. These come in pairs, 587 with STARTTLS or 465 with implicit TLS, and RFC 8314 recommends providers implement both while noting no significant difference in their security properties when the implementations are correct. Mixing the pairs produces a send that hangs rather than an error you can read, so if Mail spins and says nothing, try the other pairing before touching the credentials.
Sends, but lands in spam. The receiving server judges a message against SPF and DKIM, and those records belong to the domain in the address, which is your provider's domain. Sending through the provider's own server is precisely what keeps you aligned with those records, which is why the hostname in your settings must be the provider's own. If the alias sits on a domain you own instead, alignment becomes your job: SPF naming the provider's sending host, and DKIM signing with the key the provider issues.