SMTP relay

WordPress, Mattermost, an ERP, a printer that e-mails its scans: anything that speaks SMTP can go through Lekalao. Each message received leaves again as a transactional e-mail, logged, followed and counted.

On Lekalao’s service, the relay is smtp.lekalao.com, port 465, over SSL/TLS. On an installation of your own, its administrator runs it, and Settings → Documentation then shows its host and port.

Before you start

An API token that may write. Create it in Settings → API tokens, with Read and write. It is shown once, right after it is created: copy it then.
A verified sending domain. Add it under Deliverability and wait until it is verified (Sending domains). The software’s sender address must be on that domain: on Lekalao’s service, a message from any other domain is refused.

Connecting

Setting	Value
Host	`smtp.lekalao.com`; on your own installation, the one shown in Settings → Documentation.
Port	`465`.
Encryption	SSL/TLS from the first byte. Software calls it SSL, SSL/TLS or TLS. Never STARTTLS, never none.
Authentication	On, `PLAIN` or `LOGIN`.
User name	Anything, `lekalao` for example.
Password	The Read and write API token.
Sender address	An address on your verified sending domain, set in the software itself.

The token is revoked like any other, in Settings → API tokens. It stops working if its owner becomes a viewer or leaves the team, or, in a team that requires two-factor authentication, while its owner has set up neither a second factor nor a passkey. With a test key, every message is logged as a test e-mail, and none leaves.

Mattermost

In System Console → Environment → SMTP:

SMTP Server: smtp.lekalao.com
SMTP Server Port: 465
Enable SMTP Authentication: True
SMTP Server Username: lekalao
SMTP Server Password: the token
Connection Security: TLS

Then in System Console → Site Configuration → Notifications, set Notification From Address to an address on your verified sending domain. Without it, Mattermost sends with no sender at all, and the message is refused. Test Connection sends a real e-mail to your own address. It appears in the transactional log.

WordPress (WP Mail SMTP)

Mailer: Other SMTP
SMTP Host: smtp.lekalao.com
Encryption: SSL
SMTP Port: 465
Authentication: on, Username lekalao, Password the token
From Email: an address on your verified sending domain

Laravel or Symfony

.env

MAIL_MAILER=smtp
MAIL_SCHEME=smtps
MAIL_HOST=smtp.lekalao.com
MAIL_PORT=465
MAIL_USERNAME=lekalao
MAIL_PASSWORD=12|kJ3v8mQ2xP9…
MAIL_FROM_ADDRESS=hello@your-domain.example

For a Laravel application, the dedicated transport does more.

What goes through

Item
Recipients	Those of the envelope, 100 per message at most. Anyone in neither `To` nor `Cc` stays a blind copy.
Sender	The `From` header. An empty envelope sender (`MAIL FROM:<>`) is accepted. With no `From` header, the envelope’s address.
Subject, `Reply-To`	Read from the headers, encodings included.
Body	The HTML part, however deep it sits — a multipart inside a multipart is read through; failing that, the text part, shown as it was written.
Size	25 MB at most.
Attachments	Refused: the message is rejected with `554`. Send them through the API.

What the relay answers

Code	Means
`250 Message accepted`	Taken. It is in the transactional log.
`530 Authentication required`	Authentication is off in the software. Turn it on.
`535 Authentication failed`	Unknown or revoked token, read-only token, an owner who may not write, or one without the second factor the team requires.
`421 Too many failed attempts, closing`	Three wrong passwords on one connection: the relay closes it. The relay as a whole accepts 60 wrong passwords a minute; beyond that every login fails until the minute has passed.
`421 Too many connections, try again later`	The relay already holds as many conversations as it allows (50 by default). The software should try again a moment later.
`550 …`	Sender refused: none, or one whose domain is not a verified sending domain. The reason follows.
`554 Attachments are not relayed…`	The message carries an attachment.
`452 Too many recipients`	More than 100 recipients.
`451 Message could not be accepted`	A passing problem on Lekalao’s side. The software should try again.

When the software cannot connect

The software says	What to check
`connection refused`	Host and port. On your own installation, the relay is not running or not reachable yet: ask its administrator.
It waits, then gives up	Encryption: SSL/TLS (TLS in Mattermost), not STARTTLS and not none.
`certificate is valid for …, not smtp.…`	On your own installation, the TLS terminator in front of the relay has no certificate for its name yet: ask its administrator.
`535`, `550` or another code	The table above.

The API

Recipes

Integrations

Before you start

Connecting

Mattermost

WordPress (WP Mail SMTP)

Laravel or Symfony

What goes through

What the relay answers

When the software cannot connect

​Before you start

​Connecting

​Mattermost

​WordPress (WP Mail SMTP)

​Laravel or Symfony

​What goes through

​What the relay answers

​When the software cannot connect

Before you start

Connecting

Mattermost

WordPress (WP Mail SMTP)

Laravel or Symfony

What goes through

What the relay answers

When the software cannot connect