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Configuring SMTP+ feature in your platform and MailUp

SMTP+ users will need to first configure SMTP+ in MailUp (see Configuring Server Access and users in MailUp) and then you use the SMTP+ credentials to configure the MailUp SMTP+ in your own application/email client. Below are the various applications/email clients typically used:

Configuring applications and email clients to use SMTP+

Here are more specific instructions related to the specific email client or application you are using to connect to the MailUp SMTP+:

Configuring server access and authorized users in MailUp:

Creating a separate list

Although it's technically not a requirement, we recommend that you create a new List in your MailUp account to be used for SMTP+. Messages, statistics, and other settings will be easier to manage that way.


Within your email client, you can configure the following ports: 23, 25 , 26, 587 and all the ports from 1025 to 5000. On all the ports, you can have as an option the encryption through STARTTLS extension.

Verify your SMTP+ sender credentials

You will be asked to verify new email addresses and domains used for sending via SMTP+, MailUp's SMTP relay service. This is an email security improvement focused on limiting phishing attacks and unlawful use of your company's sending domain. Image RemovedExisting accounts have been automatically verified.

Where to find it: when adding a new account under Settings > List settings > SMTP+, you will be asked to verify new senders

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  • Once you have verified an address, remember to activate it, by checking the option Status > active user
  • It's not allowed to use SMTP+ by specifying the "from" sender from an online form. Because in this case, by definition, the sender would not be: verified and authorized.

Other features and parameters:

  • Reset password: creates a new password associated to that user. Once it has been generated, the password cannot be read in any control panel. Anyway, it is possible to reset it as many times as desired.
  • User status active: the selected user is active if the corresponding box has been checked.
  • Priority: default priority associated to the user during SMTP+ message sending. The priority used by the system will be the higher between the priority associated to the user and the priority srt during the creation of the message. You typically don't need to change this.this is the priority displayed in the email client of SMTP+ messages recipients
  • Note: You can insert here a brief note for internal use about the user that you have just created
  • Authorized domains: 
    • One or more domains authorized as senders, separated by ";" REMEMBER TO USE SEMI-COLON AND NOT A COMMA TO SEPARATE
    • All email addresses at those domains will be authorized. For example, you could enter:;
    • You can use both second level and third-level domains: for example, 2nd level domain:; 3rd level domain:
  • Authorized senders:
    • specific email addresses authorized as senders, separated by ";" REMEMBER TO USE SEMI-COLON AND NOT A COMMA TO SEPARATE
    • For example:;;

How sender authorization works

The way the system handled non-authorized messages has changed.

  • If all authorization fields are empty, all senders are authorized (i.e. both the authorized domains and authorized senders fields are empty)
  • Prior to version 8.2.4 and above, an alert was sent when a non-authorized sender was detected, as configured in the Alert Center. The message, though, was still sent.
  • With version 8.2.4 and above, a new feature was introduced that allows you to cancel the mailing if the sender is not authorized. When that feature is on and a message is sent from an unauthorized sender, the message is blocked and an alert is sent.

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Message priority

Email messages can have a priority assigned to them. For example, when you flag a message as important upon sending it from your email client, what you are doing is actually changing the priority parameter of the message.

All the messages sent from within the MailUp admin console have a default priority of 3 - normal.

By default, messages sent with SMTP+ are sent with the same priority and will be queued up together with the other messages.

You can raise the priority of the messages sent with SMTP+ using the corresponding drop-down. If messages are sent with a higher priority, they will be sent before any other messages, in first place in the sending queue. Scheduled messages or messages being sent are stopped for the time required to send the high priority messages, and then they resume when the bandwifth is available again.

Note that if you sent a priority of 1 - very high priority, the message appears differently in the email client of the receiving person.

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