Global SMTP for Outgoing Mail (Using SMTP Relay Like SMTP2GO)

himala

Hello,

I am currently setting up osTicket and trying to determine the best way to configure outbound email using a single SMTP relay service (for example SMTP2GO).

My environment is structured as follows.

Inbound Email Flow

Customers send email to our public support addresses:

support@mydomain.com
noc@mydomain.com
billing@mydomain.com

These mailboxes are hosted in Microsoft 365 and protected by spam filtering.

In Microsoft 365 we use mail flow rules (transport rules) to forward incoming messages to hidden intake mailboxes on a separate mail server used by osTicket.

Example forwarding flow:

support@mydomain.com → s1@relaydomain.com
noc@mydomain.com → n1@relaydomain.com
billing@mydomain.com → b1@relaydomain.com

The relaydomain.com mailboxes are standard IMAP mailboxes.

osTicket polls these intake mailboxes via IMAP and successfully creates tickets.
This part works correctly.

Problem: Outbound Email

Because the osTicket email objects are configured with the intake addresses (for IMAP polling), osTicket also uses those same addresses as the sender when replying to tickets.

Example outgoing email header:

From: s1@relaydomain.com

However, I want customers to receive replies from the public support addresses instead:

support@mydomain.com
noc@mydomain.com
billing@mydomain.com

I would also like to route all outbound mail through a single SMTP relay service (such as SMTP2GO) instead of configuring SMTP per mailbox.

Question

Is it possible in osTicket to configure something like the following:

Inbound IMAP mailbox:
s1@relaydomain.com

Outbound sender identity:
support@mydomain.com

SMTP relay:
smtp.relayprovider.com

In other words:

• IMAP mailbox used only for ticket intake
• Outgoing sender address different from the IMAP mailbox
• Single global SMTP relay for all outbound messages

From what I can see, osTicket appears to require the email object's address to match the sender address, which makes this architecture difficult.

Has anyone implemented a similar mail flow or found a recommended way to handle this?

Thank you.

KevinTheJedi

himala

In order to send from an email in osTicket it first has to be added as a system email; otherwise, where does it pull the address from? Once added there are two ways an Agent can send from that address:

To manually set it as the outgoing email for each Department the Agent has access to. Fun fact, you can also set a specific email as the default auto response email per-Department so all automated responses to the Users will be from that address.
To configure and enable SMTP for it.

On Agent replies the system pulls emails from the Agent’s Departments and any that have SMTP configured.

Your best bet is to configure SMTP for each email you want to send from. Otherwise you could configure an email for each Department, skip configuring SMTP, and let the system use PHPmailer/sendmail. You would then configure local send mail or postfix or something to properly route it.

Cheers.

himala

Thanks for the explanation.

The issue I’m running into is related to the way our email flow is designed.

We use Microsoft 365 for our public email addresses (support, noc, billing). Those addresses are the ones customers send email to, but they are not the mailboxes that osTicket connects to directly.

Our flow works like this.

Inbound flow

Customers send email to the public addresses hosted in Microsoft 365:

support@mydomain.com
noc@mydomain.com
billing@mydomain.com

In Microsoft 365 we use mail flow rules (transport rules) to forward those emails to hidden intake mailboxes on another mail server.

Example:

support@mydomain.com → s1@relaydomain.com
noc@mydomain.com → n1@relaydomain.com
billing@mydomain.com → b1@relaydomain.com

osTicket polls these relaydomain.com mailboxes via IMAP, and ticket creation works correctly.

The outbound problem

Because the email accounts configured in osTicket are:

s1@relaydomain.com
n1@relaydomain.com
b1@relaydomain.com

osTicket also uses those same addresses when sending replies.

So when an agent replies to a ticket, the customer receives mail from:

s1@relaydomain.com

instead of the public address:

support@mydomain.com

I attempted to configure SMTP using an SMTP relay service so that all outbound mail would go through a single relay, but osTicket still uses the email object's address as the sender address, not the public support address.

What I am trying to achieve is something like this:

Inbound IMAP mailbox:
s1@relaydomain.com

Visible sender address:
support@mydomain.com

SMTP relay:
smtp.relayprovider.com

So the intake mailbox is only used for receiving mail, while replies to customers come from the public support address.

From what I can see, osTicket requires the email object's address to match the sender address, which makes this type of architecture difficult.

Is there a supported way to separate:

the IMAP intake mailbox

the visible sender address

and a single SMTP relay for outbound mail?

Or would something like this require modifying osTicket’s mailer behavior?

Thanks.

KevinTheJedi

himala

I touched on this above but you can leave those as-is and configure your PHP mail settings with a local relay or something that can properly change the sender address based on who’s sending.

Cheers.