Email Platform Features and Limitations


Your Opalstack email service comes with the following features:

  • Secure regional access via IMAP, POP3, and SMTP protocols. Available regions are the United States and Germany, with more regions coming soon!
  • Secure access via webmail.
  • Sendmail enabled for your web applications.
  • Powerful server-side email filters via procmail.
  • Auto-responders
  • Automatic DKIM signing of outgoing mail for managed domains.
  • Platform-wide TLS encryption
  • Robust spam scanning of both incoming and outgoing mail.
  • Advanced system monitoring to stop spam attacks the moment they start.

Limitations and Restrictions

The use of your Opalstack email services comes with the restrictions and limitations detailed below.

Outgoing Mail Volume

The volume of outgoing mail sent via your Opalstack SMTP and sendmail services is limited as follows:

  • 750 messages per "day" (a rolling 24-hour period)
  • 10,000 messages per "month" (a rolling 30-day period)

If you exceed either of these limits your outgoing mail will be placed in a hold queue.

These limits apply across your entire Opalstack hosting account. If you need a higher daily or monthly limit then please contact Opalstack support for assistance.

Outgoing Mail Domains

Mail sent from your Opalstack email service can be sent only from addresses for which the domain meets the following criteria:

  1. The domain is a valid registered domain.
  2. The domain has a valid MX record.
  3. The domain has been added to the Domain List in your Opalstack control panel.
  4. If email for the recipient domain is hosted by Opalstack then the sender address must be added to the Email list in your Opalstack control panel.

If you attempt to send email from a domain that does not meet the above criteria, the message will not be delivered.

Outgoing Spam

Opalstack scans both incoming and outgoing mail for spam. If you attempt to send a message that is determined to be spam then the outgoing message will be placed on hold and you will be contacted by Opalstack support with instructions to help you resolve the issue.

Mail Storage

Mail storage quotas are as follows:

  • Managed shared hosting plan storage quotas include all of web and email storage. For example, if you have a 100GB storage quota and are using 50GB on your web server and 25GB on your mail server then you would have 25GB of available storage remaining before you reach your quota.
  • Managed VPS hosting plan storage quotas include 50GB of email storage which is separate from your VPS storage capacity.
  • Managed dedicated hosting plan storage quotas include 100GB of email storage which is separate from your dedicated server storage capacity.