Question 1

Why does Postal SMTP server fail to start or listen on IPv6 address?

Accepted Answer

Postal's current TCPServer.open only creates an IPv4 socket, ignoring IPv6 configuration. To enable dual-stack (IPv4 + IPv6) listening, modify the SMTPServer::Server listen method to explicitly open both sockets:

```ruby
["::", "0.0.0.0"].uniq.each do |addr|
  s = TCPServer.new(addr, port)
  # ...
end
```

Ensure your environment has `net.ipv6.bindv6only=0` if you need IPv4-mapped support, or set to `1` for strict IPv6-only. This fix allows binding to `::` without 'Cannot assign requested address' errors.

Question 2

How to fix 'Access denied for user postal' error when connecting Postal to MariaDB/MySQL?

Accepted Answer

Ensure the database user has ALL privileges on databases named 'postal' and 'postal-*'. Run as DB root:
```sql
GRANT ALL PRIVILEGES ON `postal`.* TO 'postal'@'%';
GRANT ALL PRIVILEGES ON `postal\_%`.* TO 'postal'@'%';
FLUSH PRIVILEGES;
```
Use 'localhost' instead of '%' if connecting locally. Verify databases exist. Details: https://docs.postalserver.io/getting-started/prerequisites#mariadb-106-or-higher

Question 3

How to stop link tracking URLs from being trimmed to 255 characters?

Accepted Answer

The link tracking database column `url` is currently set as `varchar(255)`, causing URLs longer than 255 characters to be cut off. As a workaround, manually alter the column type to `text` (or `mediumtext` if needed) in your MySQL database. For example: ALTER TABLE `your_table_name` MODIFY `url` TEXT;. No automatic migration exists yet; track the project repository for an official fix.

Question 4

How to enable SMTP submission on port 587 with STARTTLS in Postal?

Accepted Answer

Postal does not natively support changing the submission port to 587. As a workaround, use iptables to redirect port 587 traffic to port 25:
```
iptables -t nat -A PREROUTING -p tcp -m tcp --dport 587 -j REDIRECT --to-port 25
iptables -t nat -A OUTPUT -p tcp -m tcp --dport 587 -j REDIRECT --to-port 25
```
Ensure STARTTLS is enabled on port 25 for encrypted submission.

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