Updated SMTP configuration (markdown)

SMTP-configuration.md

@@ -13,7 +13,7 @@ docker run -d --name vaultwarden \
   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 explicit mode, set `SMTP_EXPLICIT_TLS` to `true` (SMTP_SSL has to be set to 'true', too). If you can send emails without logging in, you can simply not set `SMTP_USERNAME` and `SMTP_PASSWORD`.
+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 explicit mode, set `SMTP_EXPLICIT_TLS` to `true`. 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:
 
@@ -33,4 +33,72 @@ Properly configuring an SMTP server/relay isn't trivial. The mailer library that
 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](https://sendgrid.com/)
-* [MailJet](https://www.mailjet.com/)
+* [MailJet](https://www.mailjet.com/)
+
+## 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.<br>
+Also a lot of internet providers block outgoing port 25 to prevent spamming.<br>
+Most mail servers where you need to login to use either port 587, or port 465.<br>
+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.<br>
+Port 465 is SSL encrypted from the start and no plain text communication is done at all via this port.<br>
+<br>
+
+Some general settings per port.
+* for mail servers that use port 465
+  ```ini
+  SMTP_PORT=465
+  SMTP_SSL=false
+  SMTP_EXPLICIT_TLS=true
+  ```
+* for mail servers that use port 587 (or sometimes 25)
+  ```ini
+  SMTP_PORT=587
+  SMTP_SSL=true
+  SMTP_EXPLICIT_TLS=false
+  ```
+* for mail servers that do not support encryption at all.
+  ```ini
+  SMTP_PORT=25
+  SMTP_SSL=false
+  SMTP_EXPLICIT_TLS=false
+  ```
+
+### Google/Gmail
+```ini
+  # 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>
+```
+Also see: https://web.archive.org/web/20210925161633/https://webewizard.com/2019/09/17/Using-Lettre-With-Gmail/
+
+### Hotmail/Outlook/Office365
+```ini
+  # 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>
+```
+
+### Sendgrid
+Encode your api-key using base64 and use that output as your password.
+```bash
+echo -n '<YOUR_API_KEY>' | openssl base64
+```
+```ini
+  SMTP_HOST=smtp.sendgrid.net
+  SMTP_PORT=587
+  SMTP_SSL=true
+  SMTP_EXPLICIT_TLS=false
+  SMTP_USERNAME=apikey
+  SMTP_PASSWORD=<base64-encoded-api-key>
+```