What SMTP+ is and when to use it

SMTP+ is a SMTP relay service built right into your MailUp account. SMTP+ makes MailUp a truly complete email delivery solution in that you can now use it not just to create and send email marketing campaigns and triggered messages, but also to send transactional, and personal emails. For example:

  • You can configure your ecommerce store to use SMTP+ as the SMTP server to send transactional messages from the online store
  • You can set your WordPress blog to do the same
  • You can even configure your email client (e.g. Outlook) to send messages through SMTP+

The main advantages of using a service like SMTP+ are higher deliverability and tracking. Let's take a closer look...

Not for promotional campaigns

SMTP+ is not to be used for bulk promotional campaigns but only for personal or transactional messages. For more details, please contact

Transactional emails with MailUp: SMTP vs API

With MailUp you have two options when it comes to sending transactional emails:

Standard SMTP vs. MailUp's SMTP+

 Regular SMTP serverMailUp's SMTP+
DeliverabilityPotentially low (1)(star) High
StatisticsNone(star) Detailed at user level
ScalabilityLimited (2)(star) High
Header/footerMust be in the message(star) Can be automatically added
Notifications (e.g. bounces)To the sender(star) Customizable (e.g. sent to IT staff)
Triggered EmailsNone(star) Unlimited
Recipients databaseNone(star) Automatically created
UnsubscriptionsManual(star) Automated
Bounce managementManual(star) Automated
Feedback Loop managamentNone(star) Automated
Sending messages in CCNLimited(star) Unlimited. The BCC recipient receives the message with the address in the To field
Sending attachmentsLimited(star) Up to 10MB

(1) You are at the mercy of your SMTP server's reputation, which is affected by all the companies that are using it. For example, if your Web hosting company has deliverability issues, you would be negatively affected

(2) Your ISP's or Web hosting company's SMTP server is not intended for "heavy" use: it may even have volume/rate limits in place.

Higher deliverability

All emails will now go through MailUp, leveraging the system's high deliverability. Take an ecommerce Web site, for example. It typically sends emails through the Web hosting company's SMTP server. That server, however, may be used by companies that do not follow email marketing best practices, and might therefore suffer from a low reputation, with the result that emails end up in the Junk folder. Important messages such as an Order Confirmation message may never be seen by the customer. By switching to SMTP+, that online store will no longer be sending messages through the Web hosting company's SMTP server, but rather through MailUp, enjoying much higher deliverability.


Messages sent through SMTP+ are tracked. You can tell the system how to aggregate messages (e.g. based on the date, the message subject, the sender, etc.) and see 

Other information

  • List configuration: we recommend that you create a separate List for messages sent via SMTP+, or a separate account if you are sending non-bulk messages (i.e. transactional or personal emails) in order not to deliver to the "Promotions" tab in Gmail.
  • Pricing: SMTP+ is part of your MailUp account. There are no additional fees, unless you need to configure a separate account for SMTP relay.
  • Gmail "Promotions" tab: Google places most bulk messages in the Gmail "Promotions" tab: if you're sending transactional emails, you will need a different MailUp configuration to tell Gmail not to do so. This requires that you set up a separate MailUp account. Contact us if you need more information about this account configuration.

SMTP+ v2

Over the last several months we've worked hard on a new version of our SMTP relay service that would provide better performancehigher scalability, and enhanced functionality.

Version 2 of SMTP+ accomplishes all three of these goals, and becomes available to all MailUp users in June of 2015.

What's new in SMTP+ v2

Here is a short list of what's new.

Faster mailing speedThanks to a completely rethought mailing engine, messages are sent within a few seconds (compatibly with your subscribed sending speed).
MailUp merge tags supportIf the message contains merge tags (also called Dynamic fields), they are replaced with the corresponding values that exist in the MailUp account's recipient data.
Custom merge tags supportYou can include value pairs in the header of the message, and have those values replace the corresponding merge tags in the body of the message at send time.
Message schedulingIn the header of the message, you can now include a parameter that will tell the system to park the message and send it at a later time.
Message header pass-throughIf there are special headers in the message, you can contact us and ask that they are preserved (we ask you to contact us so that we can confirm that there will be no conflicts).
Better queue status reportQuickly see how many messages have been sent, how many are queued up, and how long it will take to send them.
Message-level configurations

You can now configure directly in the header of the message (and therefore at the message level) parameters such as whether a header and/or a footer should be included.

In SMTP+ v1, these parameters could only be configured at the overall List level.

Reports based on custom parameterYou can now aggregate messages based on a custom ID (e.g. a customer ID that exists in your system, not in MailUp) and therefore generate more meaningful reports.

Using SMTP+

Please refer to the following pages for details on how to...

Configuring applications and email clients to use SMTP+