In Postfix, you can restrict an email address or user from sending emails by using access control mechanisms in the Postfix configuration. Here's how you can set it up:
### 1. Use `smtpd_sender_restrictions`
Postfix allows you to define rules to control which senders are allowed or denied. To restrict sending emails for a specific address, you can use the `smtpd_sender_restrictions` parameter in the Postfix configuration.
#### Steps:
1. **Edit the Postfix Main Configuration File:**
Open the Postfix main configuration file, usually located at `/etc/postfix/main.cf`, with a text editor of your choice:
```sh
sudo nano /etc/postfix/main.cf
```
2. **Add or Modify `smtpd_sender_restrictions`:**
Add or update the `smtpd_sender_restrictions` parameter to include a reference to a new file where you will specify the restrictions. For example:
```plaintext
smtpd_sender_restrictions = check_sender_access hash:/etc/postfix/sender_access
```
3. **Create or Edit the `sender_access` File:**
Create or edit the file specified in the `smtpd_sender_restrictions` parameter, which in this case is `/etc/postfix/sender_access`:
```sh
sudo nano /etc/postfix/sender_access
```
4. **Add Restriction Rules:**
Add a rule to block sending for the specific email address. For example, to block `
user@example.com`:
```plaintext
user@example.com REJECT
```
5. **Update Postfix with the New Access File:**
After modifying the `sender_access` file, you need to hash the file and reload Postfix:
```sh
sudo postmap /etc/postfix/sender_access
sudo systemctl reload postfix
```
### 2. Using `smtpd_recipient_restrictions`
Alternatively, you can use `smtpd_recipient_restrictions` to block specific senders if your setup uses that parameter.
#### Steps:
1. **Edit the Postfix Main Configuration File:**
Open the Postfix main configuration file:
```sh
sudo nano /etc/postfix/main.cf
```
2. **Add or Modify `smtpd_recipient_restrictions`:**
Add or update the `smtpd_recipient_restrictions` parameter:
```plaintext
smtpd_recipient_restrictions = check_recipient_access hash:/etc/postfix/recipient_access
```
3. **Create or Edit the `recipient_access` File:**
Create or edit the file specified in the `smtpd_recipient_restrictions` parameter:
```sh
sudo nano /etc/postfix/recipient_access
```
4. **Add Restriction Rules:**
Add a rule to block sending for the specific email address:
```plaintext
user@example.com REJECT
```
5. **Update Postfix with the New Access File:**
Hash the file and reload Postfix:
```sh
sudo postmap /etc/postfix/recipient_access
sudo systemctl reload postfix
```
### Summary
By using either `smtpd_sender_restrictions` or `smtpd_recipient_restrictions`, you can effectively block a specific email address from sending messages. Ensure you adjust your configuration based on whether you want to block sending globally or for specific users. Always reload Postfix after making changes to ensure that your new settings take effect.
Aber das mit smtpd_sender_restrictions werde ich mal versuchen.
