smtp - Mailster Knowledge Base

Send your Newsletters via SendGrid

SendGrid is a powerful sending provider that works with Mailster.

Send your Newsletters via SparkPost

With SparkPost you get a solid delivery provider. There’s some setup required before you can use this service though. SparkPost no longer offers a free tier but you can test their service with a “Test Account”.

Mails are send but not delivered

When Mailster sends an email via your chosen delivery method it always relies on the response of your sending server. Sometimes the message has been sent but not actually delivered.

SMTP Error: data not accepted

This error occurs if you’re sending via SMTP. The SMTP server rejects the mail for several reasons: Your server doesn’t allow different sender and usernames Some servers require that the From email address is the same as the email address used to authenticate. Check your from-name and match it to the username you use to […]

SMTP Error: Could not connect to SMTP host.

Whenever you get a connection error when sending via SMTP like The most common reason for this problem is that the ESP (Email service provider) you have defined in your delivery settings doesn’t accept one of the used email addresses.

How can I send newsletters via GoDaddy?

Although it’s not recommended to use GoDaddy’s own email servers, you can do it, but you have to follow some rules: GoDaddy has a limit of 500 emails sent via SMTP from a certain account so make sure you set up the sending limits correctly. You have to make sure the from and reply-to address […]

SMTP Error: Could not authenticate

In some cases your campaign pauses or you are even not able to send emails at all cause of this error: You can also try to pause your campaign and resume it after a while if it’s a temporary problem.

Why can’t I use SMTP?

SMTP (Simple Mail Transfer Protocol) uses different ports to send emails. Sometimes your provider blocks specific ports and you’re not able to send via SMTP. Some providers also allow only sending via their own SMTP server and block others completely.