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GoAdmio Documentation

Roundcube Custom SMTP

From the GoAdmio knowledge base.

Roundcube Custom SMTP

This page explains the Roundcube Custom SMTP feature in GoAdmio. It lets a single hosting account override the server-wide Roundcube SMTP relay and use its own SMTP server — affecting only that account's Roundcube webmail, not other accounts and not other mail clients.

Location: Admin Panel → Email → Roundcube Custom SMTP
Location (User Panel): Email → Roundcube Custom SMTP (if enabled for the account)


Overview

Roundcube Global SMTP configures one relay for every Roundcube user on the server. Roundcube Custom SMTP is a per-account override of that global setting.

When a custom SMTP is configured for an account:

  • That account's Roundcube users send mail through their own SMTP relay, not the global one
  • Every other account on the server continues to use the global Roundcube SMTP relay
  • SnappyMail, Outlook, Thunderbird, and other mail clients are unaffected — this setting only changes Roundcube
This is useful when:
  • A customer has their own transactional email provider (e.g., SendGrid, Mailgun, Amazon SES) and wants webmail to use it
  • A customer's sending volume needs a dedicated relay with its own rate limits
  • A reseller wants their accounts to send through their own relay, separate from the host's
  • A specific account needs a different From address or sender domain than the global relay enforces
> Note: This page applies only to Roundcube. For a server-wide relay, see Custom SMTP Relay. For the server-wide Roundcube relay, see Roundcube Global SMTP. For external mail clients, the user configures SMTP in their own client.

Precedence: Which Relay Is Used?

When a Roundcube user sends mail, GoAdmio checks settings in this order:

| Priority | Setting | Affects |
|---|---|---|
| 1 (highest) | Roundcube Custom SMTP (this page) | That account's Roundcube only |
| 2 | Roundcube Global SMTP | All Roundcube users on the server |
| 3 (lowest) | Local Postfix (default) | Roundcube sends via port 25 directly |

> Tip: If a custom SMTP is set for an account, it always wins over the global setting — even if the global setting is changed later. Remove the custom SMTP to make the account fall back to the global relay.


Roundcube Custom SMTP vs. Other Relay Pages

| Page | Scope | Affects |
|---|---|---|
| Custom SMTP Relay | Server-wide | All outgoing mail from every domain (Postfix) |
| Roundcube Global SMTP | Server-wide | All Roundcube users |
| Roundcube Custom SMTP (this page) | Per account | Only that account's Roundcube |
| Global SMTP Relay | Admin only | The server administrator's mail |
| Brevo API | Per domain | Brevo integration for a domain |


Prerequisites

Before configuring Roundcube Custom SMTP for an account:

  1. Roundcube is installed on the server. See Webmail.
  2. The account exists and is active. See List Accounts.
  3. The customer's SMTP provider account exists with credentials ready.
  4. The sending domain is verified at the provider, and SPF/DKIM records are in place. See SPF / DKIM.
  5. Outbound port 587 (or 465) is open in the server firewall.
  6. The account's package allows custom SMTP (some hosts restrict this). See Add/Modify Packages.
> Tip: If the customer does not have their own relay, leave this page blank so the account uses the global Roundcube SMTP relay. See Roundcube Global SMTP.

How to Configure Roundcube Custom SMTP

Via the Admin Panel

  1. Log in to the GoAdmio Admin Panel.
  2. Navigate to Email → Roundcube Custom SMTP.
  3. Select the account (search by domain or username).
  4. Fill in the custom relay details:
| Field | Description | Example | |---|---|---| | SMTP Host | The relay server hostname | smtp.sendgrid.net | | SMTP Port | 587 (STARTTLS) or 465 (SSL/TLS) | 587 | | Encryption | STARTTLS, SSL/TLS, or None | STARTTLS | | SMTP Username | Provider SMTP username | apikey | | SMTP Password | Provider SMTP password or API key | SG.... | | From Address | Envelope sender address (must be verified at the provider) | noreply@customerdomain.com | | From Name | Display name for outgoing mail | Customer Name | | Authentication Required | Usually Yes | Yes |
  1. Click Save.
  2. Optionally click Test to send a test message from the account's Roundcube.
The custom settings are written to that account's Roundcube configuration and take effect immediately for its users.

Via the User Panel

If enabled for the account:

  1. Log in to the User Panel.
  2. Navigate to Email → Roundcube Custom SMTP.
  3. Enter the SMTP details.
  4. Click Save.
> Note: Feature availability in the User Panel depends on the account's package and the admin's permission settings.

What Changes

| Item | Changes? | Notes |
|---|---|---|
| That account's Roundcube sending | ✅ Yes | Uses the custom relay |
| Other accounts' Roundcube sending | ❌ No | Continue using the global relay |
| SnappyMail sending | ❌ No | Separate configuration |
| Outlook / Thunderbird / mobile apps | ❌ No | Client-side SMTP settings |
| Postfix server-wide relay | ❌ No | See Custom SMTP Relay |
| Incoming mail | ❌ No | Still delivered to local Postfix/Dovecot |
| Email account passwords | ❌ No | Unchanged |

> Note: Only the sending path for that account's Roundcube users changes. Incoming mail and IMAP/POP3 access remain unchanged.


How It Works

When a user of the account logs in to Roundcube and sends a message:

  1. Roundcube reads that account's custom SMTP configuration (overriding the global).
  2. Roundcube connects directly to the custom relay and authenticates.
  3. The relay accepts the message and delivers it.
  4. The message bypasses local Postfix for the outbound leg.
Other accounts continue to use the global Roundcube SMTP relay (or local Postfix if no global relay is set).

Verify the Configuration

Check the account's Roundcube configuration

GoAdmio stores per-account Roundcube settings in the account's configuration directory. For example:

```bash

Adjust the path to match your GoAdmio/Roundcube layout


grep -E "smtp_(server|port|user)" /home/<username>/.roundcube/config.inc.php

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