Sending Emails

Owned by Timo Fuchs
Last updated: Juni 02, 2020
3 min read

Choosing your Email servers or platform

If you are planning to use the Universal Messenger to send Email newsletters thousands or even millions of Emails will be sent every month. Since most receiving Email providers have rules to distinguish between legitimate mass marketing Emails and plain SPAM it is very important to know and follow them.

You have to carefully manage your Mail server’s and your domain name’s reputation. With a bad reputation

  • you will not be able to reach all of your recipients, some Email providers like Gmail or Outlook may even block your Mail server or your domain name entirely.

  • you may not even be able to send your regular company Emails any more if you are using the same Domain name or Mail server as your mass Emails.

We have compiled a list of best practices here: Deliverability - how to manage your Email reputation .

Email delivery providers

You can not only use a regular SMTP server to send your Emails. The Universal Messenger also supports a number of cloud Email delivery providers like:

They use web services to deliver Emails and also use different methods for bounce management.

Sender address

There can be a difference between the technical sender address and the address given in the FROM header. The technical sender address is called “Envelope sender” or “Return path”. It will show in the Email header under “Return-path”. The FROM address is shown in the recipient Email application, i.e. what the recipient can see.

That means:

  • If a mail server sends a reply it will use the envelope sender address

  • If a recipient replies using their Email application it will use the FROM (or REPLY-TO) address.

Therefore it makes sense to use different addresses in order to separate technical replies from “real” replies.

The envelope sender address must be a valid Email address and you must have access to the mailbox which receives Emails to that address. It will be used for all technical purposes.

The Universal Messenger supports the following sender address options and can be configured in cmsbs.bounce.verp.envelopeFrom:

VERP (Variable Envelope Return Path)

  • Sender address consists of a static and a variable part, e.g. newsletter-ABC1235XYZ@mydomain.com.

  • You can define the pattern in cmsbs.bounce.verp.envelopeFrom as newsletter-%@mydomain.com

  • Your mail server must be able to put all received Emails matching that pattern into the same mailbox. Whether this is possible or not depends on the mail server software used.

    • Usually works: Exim/courier, postfix/dovecot

    • Usually doesn’t work: Exchange, Lotus Domino/Notes

      • Workaround: Catch-All rule for subdomain

  • The Universal Messenger will create a unique pattern as the variable part for every single Email it sends out and keeps a record to remember which address was used for which Email.

Details: https://www.universal-messenger.de/knowledge-base/intern/doc-en/Developer/Bounce_management_by_VERP.html

Static envelope sender address

Sender address is fixed and will be used for every Email sent by Universal Messenger regardless of which address is set in FROM header. In that case, just set that Email address in property cmsbs.bounce.verp.envelopeFrom.

Use FROM address

If you do not define a technical sender address the one used in the FROM header will be used by default. Note that if this address will receive all technical messages like vacation replies or bounce messages. For this option do net set property cmsbs.bounce.verp.envelopeFrom.

Bounce management

It is important to detect whether a single Email could be delivered and find out the reasons why not. If an Email cannot be delivered your mail server will usually get a reply: a bounce message.

The following types of bounces are recognized:

  • Hard bounce: The recipient Email address does not exist

  • Soft bounce: The Email could not be delivered due to a temporary problem, e.g. recipient mailbox is full.

  • Autoresponder: The Email was delivered but an automatic response was sent, e.g. a vacation notice.

All bounce messages will be sent to the technical sender address (see above).

Details: https://www.universal-messenger.de/knowledge-base/intern/doc-en/Developer/Bounce_management.html

Reading and evaluating bounce messages

In order to read and evaluate those messages it is necessary to give the UM access to the mailbox. You can use either POP3 or (better) IMAP.

The Universal Messenger will automatically determine the type of bounce and which recipient address is affected.

  • If you are using VERP the UM will know for exactly which Email sent the message was replied to, based on the variable sender address.

  • If you are not using VERP the UM will analyze the bounce message using complex recognition patterns to find the matching Email address.

If the UM cannot find a type or a matching Email address it will forward the Email to a postmaster address defined in the global UM configuration.

Automatically unsubscribe users with too many bounces

The Universal Messenger can automatically unsubscribe users from all lists if their Email address has too many bounces. It is also possible to give a CSE callback function if the threshold is reached.

  • cmsbs.bounce.hardbounce.max = <number>

  • cmsbs.bounce.softbounce.max = <number>

  • cmsbs.bounce.autorespond.max = <number>