The SMTP API allows developers to implement Sendinc’s email encryption service into their application in minutes – using the standard SMTP protocol over TLS/SSL or STARTTLS.
To get started, all you will need is a Sendinc account. A free account can be created here. The API can be used by Sendinc Basic, Sendinc Pro, and Sendinc Corporate users. However, some functionality is limited to only Sendinc Pro and Sendinc Corporate accounts.
The Process
Using the SMTP API is easy. You just need to point your application to relay mail to Sendinc’s secure SMTP servers:
SMTP Server: smtp.sendinc.net\n
SSL/TLS Port: 465\n
STARTTLS Port: 366 or 586\n
Username: YourEmail@example.com [OR] SendincEmailAlias@secure25.net\n
Password: YourSendincPasswordSendinc will then encrypt your message and send the secure message notification to your recipients. Be sure to check out our SMTP Integration articles for step-by-step setup guides:
Advanced Features
Subject line flags can apply Additional functionality and controls to your messages. Recipients will not see the flags in the subject when they receive the message.
| Flag | Description | Default |
| [notify] | (Pro/Corporate Only) Receive an email notification when a recipient opens your message. | false |
| [expire-when-read] | (Pro/Corporate Only) Set the message to expire after the recipient reads it. | false |
| [expires:7] | (Pro/Corporate Only) Set an expiration date (in days) for your message to expire. Valid ranges include 1-365 days and 0 for no expiration date. | 7 for Basic accounts, 0 (never) for Pro/Corporate accounts. |
| [copy-me] | Send a copy of the message to the sender. | false |
Sample Subject with Flags:
This is an email subject line [notify] [expires:90] [copy-me]X-Headers
Additional functionality and controls can be applied to your messages using X-Headers.
| X-Header | Description | Default |
| X-Sendinc-Notify | (Pro/Corporate Only) Receive an email notification when a recipient opens your message. | 0 (false) |
| X-Sendinc-Expire-When-Read | (Pro/Corporate Only) Set the message to expire after the recipient reads it. | 0 (false) |
| X-Sendinc-Expires | 7 for Basic accounts, 0 (never) for Pro/Corporate accounts. | 7 for Basic accounts, 0 (never) for Pro/Corporate accounts. |
| X-Sendinc-Copy-Me | Send a copy of the message to the sender. | 0 (false) |
Masquerading (Corporate Accounts Only)
For Sendinc Corporate accounts with multiple users it’s not necessary to possess the authentication credentials for each of your users in order to use the SMTP API. Simply authenticate using the Sendinc account of a Sendinc Corporate administrator (defined in the Sendinc Corporate management console) and indicate the Sendinc Corporate user you wish the message to originate from by specifying their email address as the from address.
Error Handling
During normal operations the SMTP server will return 2XX response codes. In the event of an error the server will return 4XX or 5XX response codes along with an error message (ex: “421 4.7.1 Secure connection required”). Your application should anticipate these error codes and respond accordingly.
Rate Limits
To ensure a consistent quality of service Sendinc may block users making a large number of requests over a short period of time. Most users will never come close to reaching this limit but if it is reached the server may temporarily refuse additional connections from you.
Still have questions about the Sendinc SMTP API?