---
title: "Introduction"
slug: "introduction-to-mail-and-deploy-expressions"
updated: 2026-10-08T13:14:23Z
published: 2026-10-08T13:14:23Z
canonical: "help.mail-and-deploy.com/introduction-to-mail-and-deploy-expressions"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.mail-and-deploy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction to Mail & Deploy Expressions

### General

Expressions are formulas that can dynamically evaluate values at runtime; they allow to return static or dynamically calculated values.

**Example:** Let's suppose you design a [Report](/release34/docs/introduction-to-reports) and you use a [Filter Datasource Field Action](/release34/docs/filter-datasource-field) to filter a field. The values to which you filter the field are expressions which can be used to either return constant values or dynamic values (e.g. the current year, the previous year etc.).

### Syntax

Mail & Deploy expressions are written in  [Visual Basic .NET](https://learn.microsoft.com/en-us/dotnet/visual-basic/); however, there are many additional functions provided by Mail & Deploy which are not part of the standard Visual Basic .NET language.

### Expression Fields

You can enter expressions in all expression fields which can be identified in the following way:

### Web User Interface

An expression field in the web user interface (accessed by your web browser) looks like this:

![](https://cdn.document360.io/e3657e0f-d0b6-4032-8271-1f5869a7b807/Images/Documentation/image%2835%29.png) **Expression Editor**

The  button in the expression editor can be used to insert a [Placeholder](/release34/docs/introduction-to-placeholders) or other value into the expression. Report Designer Expression fields in the [Report Designer](/release34/docs/report-designer) look like this:

![](https://cdn.document360.io/e3657e0f-d0b6-4032-8271-1f5869a7b807/Images/Documentation/image%2836%29.png) **Expression Field in the Property Grid**

Another form of expression field in the designer looks like this:

![](https://cdn.document360.io/e3657e0f-d0b6-4032-8271-1f5869a7b807/Images/Documentation/image%2837%29.png) **Expression Field**

By clicking the three-dot browse button you can open the expression editor for that expression.

![](https://cdn.document360.io/e3657e0f-d0b6-4032-8271-1f5869a7b807/Images/Documentation/image%2838%29.png) **Expression Editor**