Identities allow you to specify a bunch of options for how you send mail through your Fastmail account.

They allow you to control how you appear if you want to send mail through Fastmail on behalf of one of your other external mail accounts, as well as from Fastmail itself.

To manage identities:

  1. Open the Settings → Identities & Fetch screen.
  2. Your list of identities will be displayed under the "Send Mail As" heading. Use the Edit button to edit an identity, or use the Add Identity/Fetch button in the toolbar at the top to create a new one.
  3. Don't forget to Save when you're done.

If you specify *@domain.tld for an account identity email address, then you will be able to specify something different to replace the * with for each individual message that you send using this identity.

Identity options

Each identity has a number of options associated with it:

Advanced Options

Extra tips and tricks

If you just want to use an identity for BCC on 3rd party clients or Save a copy on 3rd party clients, you can put a single * as the left side of the email address before the @ to make it match anything. For instance, * will match any email address you send with. If you have an identity with a specific email address that matches a From address, that will take precedence; * matches will only occur as a fallback.

Identities and SPF

SPF was an attempt to reduce spam by stopping people forging the domain in the SMTP MAIL FROM envelope of sent email.

Unfortunately SPF has not reduced spam at all because: a) no user ever sees the SMTP MAIL FROM envelope, so it doesn't stop spammers forging the From header users see in emails, and b) anyone can set up SPF on any domain they own, and SPF doesn't tell you which domains to actually trust.

Whether the SPF checks pass or fail has little correlation with whether a message is spam or not. We can see this in the SpamAssassin scores, which show that SPF failures have quite a low score.

score SPF_PASS -0.001
score SPF_FAIL 0 0.919 0 0.001 # n=0 n=2
score SPF_NEUTRAL 0 0.652 0 0.779 # n=0 n=2
score SPF_SOFTFAIL 0 0.972 0 0.665 # n=0 n=2

Additionally, SPF breaks the simple forwarding of emails between systems, and requires a separate system called SRS to rewrite the SMTP MAIL FROM envelope and to forward bounces back through the forwarding system.

Despite that, some systems treat SPF failures as a sign of spaminess, so you may want to make sure your sent emails pass SPF tests. If you are sending email with a From address from a domain that's not hosted with Fastmail and doesn't have specific SPF records authorising our servers, you should send via that domain's SMTP server instead, using the Send messages using an external SMTP server option.