An alias is another email address associated with your account so that email to that address ends up in your accounts mailbox. An alias is not an entire separate account; it's just another way to send email to an account.
Why is this useful? A few reasons:
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You can use different email addresses for different groups/people, and then ensure that email sent to those different addresses are automatically filed into different folders, so you can keep them separate.
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You can create an alias for signing up to newsletters, or web sites, etc, and if it starts getting too much spam, you can delete the alias.
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You can completely hide your account name so no-one can ever even attempt to login to your account. For instance, if you create your account as trickyaccountname@fastmail.fm, but create an alias of myaddress@fastmail.fm and only tell people about myaddress@fastmail.fm, then people can send you email to myaddress@fastmail.fm, but myaddress@fastmail.fm won't exist as a login name people can try and login to or hack; only trickyaccountname@fastmail.fm which you don't tell anyone about can be used to login to your account.
So when you want to create a new email address, you have 2 main options:
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Signup a brand new account. This gets a new username, it's own login password, it's own separate mailbox, sending limits, etc.;
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Create an alias under an existing account. This gets a new address to send email to (e. g. newalias@fastmail.fm), but email still goes to an existing account.
Now when email arrives for a particular alias, it really just gets redirected to the alias "target". So if you create newalias@fastmail.fm you have to target it somewhere, namely, youraddress@fastmail.fm.
An alias target is just the email address (or addresses) to actually send the email to that matches that alias.
By default, the target of all aliases is your account name, so email sent to an alias instead is sent to your account.
You can however change the target of an alias to be any other account, including other FastMail.FM accounts or a completely external email address.
You can target multiple accounts just by using a comma-separated list of email addresses. If you do that, a copy of each email will be delivered to each target address. This can be a useful way to direct a copy of all email to a separate backup account at another provider if you want. To do that, create an account and setup an alias that targets both your account, and the external account you want backups to go to. Then when you tell people about your email address, tell them your alias address, never your account's address.
You can also change targets to use plus addressing. Commonly, you might want email sent to a particular alias to go into a certain folder. The easiest way to do this is to use plus addressing with the target. So if you have a folder 'aliasmessages', you can set the target to 'youraddress+aliasmessages@fastmail.fm', and any email sent to the alias will automatically be put in the 'aliasmessages' folder.
One thing to note is that alias targeting occurs before any rules or spam scanning is applied to a message.
FastMail.FM allows you to setup 'aliases', so that emails sent to another email address end up in your accounts mailbox.
An alias is both a name and domain combination, e. g. me@fastmail.fm or you@eml.cc. For normal aliases, the domain must be one of the ones we own (e. g. fastmail.fm, etc.).
You can also setup 'virtual domains'. In this case, FastMail.FM will accept email for an entire domain and target it to selected accounts for you. See Own Domains, Activating for more details.
On the aliases screen, there is an SRS checkbox for each alias. This can be useful if you have an external (eg. non FastMail.FM email address) target for one of your aliases, and the target server you're forwarding to uses SPF to block emails.
Basically SPF is a way for domain owners to authorise only particular servers to send email with a particular SMTP MAIL FROM envelope. The problem is that when email is forwarded by a service, the SMTP MAIL FROM envelope should be preserved. When that happens, it looks like the forwarding service is trying to send email with the same SMTP MAIL FROM envelope as the original service, which is blocked because the forwarding service hasn't been authorised. This is a bug with the design of SPF. There is a (fairly ugly) way to work around this though, and it's called SRS rewriting.
You can enable SRS rewriting for email sent to a particular alias just by enabling the SRS checkbox on that alias. We don't recommend this unless you need to (eg. emails aren't forwarded correctly).
To get an idea of what SRS is, and what it does, here's a description:
Say I have an alias abc@fastmail.fm that targets xyz@gmail.com
Someone sends an email from their hotmail account def@hotmail.com to abc@fastmail.fm. So the email has a SMTP MAIL FROM envelope of def@hotmail.com and a SMTP RCPT envelope of abc@fastmail.fm
We accept the email, and see it's an alias with target xyz@gmail.com. We forward the email with the SMTP RCPT TO envelope of xyz@gmail.com, and by default preserve the SMTP MAIL FROM envelope of def@hotmail.com.
However at this point, gmail looks at the SMTP MAIL FROM envelope, sees @hotmail.com, does an SPF check and says "hold on, 66.111.4.25 (one of FastMail.FM's outgoing IPs) hasn't been authorised by SPF to send email with an SMTP MAIL FROM envelope of @hotmail.com". SPF has broken forwarding.
When you activate SRS, we change the following.
We accept the email, and see it's an alias with target xyz@gmail.com. We forward the email with the SMTP RCPT TO envelope of xyz@gmail.com, and we alter the SMTP MAIL FROM envelope of def@hotmail.com to use SRS rewriting which creates something like SRS0+abcd=Cw=hotmail.com=def@srs.messagingengine.com. Since @srs.messagingengine.com is a domain we control, so there's no SPF issue.
If for some reason the email ends up bouncing, the NDN will be sent back to SRS0+abcd=Cw=hotmail.com=def@srs.messagingengine.com, which we'll get, and then unwrap back to def@hotmail.com and send the NDN there.
The number of included aliases and virtual domain hosts depends on your service level .
- Guest: No aliases or virtual domains allowed
- Ad-free: Two aliases allowed. The alias name must be the same as the login name, but at a different FastMail.FM domain.
- Full: You can have up to 6 other aliases in any FastMail.FM domain. Each name must be 5 characters or more. You may also have 1 alias of less than 5 characters.
- Enhanced: You can have up to 100 other aliases in any FastMail.FM domain. Each name must be 5 characters or more. You may also have 3 aliases of less than 5 characters.
In addition to these aliases, there are also 'virtual domain' aliases. Only Enhanced accounts may use virtual domains. Enhanced accounts include 50 free virtual domains, and 200 free virtual aliases within those hosted domains.
See our pricing table for full details.