SMTP Configuration

You can configure vaultwarden to send emails via a SMTP agent:

docker run -d --name vaultwarden \
  -e SMTP_HOST=<smtp.domain.tld> \
  -e SMTP_FROM=<[email protected]> \
  -e SMTP_PORT=587 \
  -e SMTP_SSL=true \
  -e SMTP_USERNAME=<username> \
  -e SMTP_PASSWORD=<password> \
  -v /vw-data/:/data/ \
  -p 80:80 \
  vaultwarden/server:latest

When SMTP_SSL is set to true(this is the default), only TLSv1.1 and TLSv1.2 protocols will be accepted and SMTP_PORT will default to 587. If set to false, SMTP_PORT will default to 25 and the opportunistic encryption will be tried (no encryption attempted with code prior to 3/12/2020). This can be very insecure, use this setting only if you know what you're doing. To run SMTP in implicit (forced TLS) mode, set SMTP_EXPLICIT_TLS to true (Hint: environment-variable is mislabelled, see bug #851). If you can send emails without logging in, you can simply not set SMTP_USERNAME and SMTP_PASSWORD.

Note that if SMTP and invitations are enabled, invitations will be sent to new users via email. You must set the DOMAIN configuration option with the base URL of your vaultwarden instance for the invite link to be generated correctly:

docker run -d --name vaultwarden \
...
-e DOMAIN=https://vault.example.com \
...

User invitation links are valid for 5 days, after which a new invitation will need to be sent.

SMTP servers

Properly configuring an SMTP server/relay isn't trivial. The mailer library that vaultwarden uses also isn't the easiest to troubleshoot. So unless you're particularly interested in setting this up yourself, it's probably easier to use an external service.

Here are a few services with a free tier that allows sending 100-200 emails per day (which is plenty for most use cases):

• SendGrid
• MailJet

Here some sane defaults for well known services

General

Mail servers listen on port 25 mostly only to accept mail from other mail servers, and only for mail which they are the final location.
Also a lot of internet providers block outgoing port 25 to prevent spamming.
Most mail servers where you need to login to use either port 587, or port 465.
Port 587 is called the submission port, and can most of the time only be when using a username and password. Port 587 starts off unencrypted and upgrades to a TLS encrypted connection during the communication between client and server.
Port 465 is SSL encrypted from the start and no plain text communication is done at all via this port.

Some general settings per port.

• for mail servers that use port 465

  SMTP_PORT=465
  SMTP_SSL=false
  SMTP_EXPLICIT_TLS=true

• for mail servers that use port 587 (or sometimes 25)

  SMTP_PORT=587
  SMTP_SSL=true
  SMTP_EXPLICIT_TLS=false

• for mail servers that do not support encryption at all.

  SMTP_PORT=25
  SMTP_SSL=false
  SMTP_EXPLICIT_TLS=false

Google/Gmail

You need to generate a App Password for Vaultwarden to work with Gmail.
Follow the steps here: https://support.google.com/accounts/answer/185833?hl=en&ref_topic=7189145
In the end you well be shown a password (with spaces in between which are not there, it is just for easy type-over), us this password.
FullSSL:

  # Domains: gmail.com, googlemail.com
  SMTP_HOST=smtp.gmail.com
  SMTP_PORT=465
  SMTP_SSL=false
  SMTP_EXPLICIT_TLS=true
  SMTP_USERNAME=<mail-address>
  SMTP_PASSWORD=<less-secure-app-password>

StartTLS:

  # Domains: gmail.com, googlemail.com
  SMTP_HOST=smtp.gmail.com
  SMTP_PORT=587
  SMTP_SSL=true
  SMTP_EXPLICIT_TLS=false
  SMTP_USERNAME=<mail-address>
  SMTP_PASSWORD=<less-secure-app-password>

Also see: https://web.archive.org/web/20210925161633/https://webewizard.com/2019/09/17/Using-Lettre-With-Gmail/

Hotmail/Outlook/Office365

  # Domains: hotmail.com, outlook.com, office365.com
  SMTP_HOST=smtp-mail.outlook.com
  SMTP_PORT=587
  SMTP_SSL=true
  SMTP_EXPLICIT_TLS=false
  SMTP_USERNAME=<mail-address>
  SMTP_PASSWORD=<password>
  SMTP_AUTH_MECHANISM="Login"

Sendgrid

Replace <full-api-key> with the generated API-Key from SendGrid which starts with SG.
Also make sure the API-Key has full Mail Send rights, else you can't login with this key.
StartTLS:

  SMTP_HOST=smtp.sendgrid.net
  SMTP_PORT=587
  SMTP_SSL=true
  SMTP_EXPLICIT_TLS=false
  SMTP_USERNAME=apikey
  SMTP_PASSWORD=<full-api-key>
  SMTP_AUTH_MECHANISM="Login"

Full SSL:

  SMTP_HOST=smtp.sendgrid.net
  SMTP_PORT=465
  SMTP_SSL=false
  SMTP_EXPLICIT_TLS=true
  SMTP_USERNAME=apikey
  SMTP_PASSWORD=<full-api-key>
  SMTP_AUTH_MECHANISM="Login"

Passwords with special characters

If you want to use some special characters within your password, it could be that you need to escape some of these characters to not confuse the environment variable parsers.
For example a \ or ' or " can be used, but sometimes they need to be escaped so that they are actually used. It is probably best, if you use special characters, to always use single quotes around the password.
Lets take the following password as an example: ~^",a.%\,'}b&@|/c!1(#}
Here are a few characters which could break the environment variable parses like, \, ' and ". A single \ is normally used to escape other characters, so if you want to use a single \, you need to type \\.
Also, the quotes ' and " could cause some issues, so lets enclose this password within single quotes and escape the special characters.
To have the password above to work we need to type '~^",a.%\\,\'}b&@|/c!1(#}', here you see that we escaped both the \ and the ' characters and used single quotes to surround the whole password. So: ~^",a.%\,'}b&@|/c!1(#} becomes '~^",a.%\\,\'}b&@|/c!1(#}'