SMTP quota

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DreamHost Enforces Outbound Mail Limits/Quotas

In our effort to combat the ever increasing problem with Unsolicited Bulk E-mail (UBE) a.k.a. "SPAM" we reserve the right to limit the number of recipients per hour customers can send e-mail messages to.

Q: How does this help?

A: The better we can limit the amount of spam originating from our systems (and spam forwarded through our systems) the less likely our servers will be black/gray listed by other ISPs and e-mail services. This in turn allows us to provide more reliable service to our customers (you!).

While trying to send mail, if you receive an error message which says "SENDER_QUOTA_REJECTION" that means that you have exceeded, or attempted to exceed your mail sending limit for that particular account. Also, if you attempt to send messages and do not use the correct FROM address the system will also give you this error and will not send your message.

Default Sending Limits/Quotas

  • SMTP Authentication (regular) e-mail accounts: 100 recipients per hour
    • Max recipients per message: same as sending limit
    • Max message size: 40MB (encoded)
  • SMTP Authentication (webmail) e-mail accounts: 100 recipients per hour
    • Max recipients per message: same as sending limit
    • Max message size: 10MB (PHP max upload limit) for SquirrelMail and RoundCube
  • FTP/shell accounts (sending using scripts via PHP/CGI, etc.): 200 recipients per hour
    • Max recipients per single message: 40
    • Max message size: 40MB (encoded)
  • DreamHost "Announce Lists" (configured via our control panel): unlimited recipients per hour
    • Max recipients per message: unlimited
    • Max message size: 40MB (encoded)

Notice that these limits are based on the number of RECIPIENTS, not the number of messages! A single e-mail message with 5 recipients would count as 5 towards your sending limit.

All recipients in the TO, CC and BCC fields are counted.


  1. If you sent a single message with 100 recipients (for SMTP accounts) that would max out your sending limit for that hour. After one hour you could attempt to send more messages.
  2. If you were to send 5 messages with 5 recipient each during one hour the system would count this as 25 recipients during that hour.
  3. If you sent 100 messages with a single recipient each (for SMTP accounts) that would max out your sending limit for that hour.
  4. If you have already sent messages to 50 recipients and then within that same hour tried to send another message with 55 recipients; that second message will FAIL and your account will be blocked because it would have exceeded your sending limit. You would have to wait for that hour to elapse (from the time you send the first message) before you could attempt to resend the message which could not be sent during the last hour.

Once you have reached your hourly sending limit any message that you attempt to send that would exceed your sending limit will cause your account to be blocked immediately. Those messages that exceeded, or attempted to exceed, your sending limit would NOT be sent and would fail with a "SENDER QUOTA REJECTION" error message. Those unsent messages would typically remain in your e-mail client's "outbox" so that you could attempt to resend them later.

However, the mail servers will AUTOMATICALLY unblock/reset your account one hour after the first message that was sent. There is no need to contact support when this happens.

If you attempt to send a message that exceeds the maximum number of recipients it will always cause your account to be blocked!

Accounts that are blocked repeatedly for attempting to exceed their sending limit will be blocked permanently by the system. They will be required to contacts technical support for assistance in order to have their account unblocked. In your support request, please include your email username and email address.

Although a messages that may have been successfully sent to a recipient may "bounce" back to you for various reasons, it still counts towards your sending limit. They are not deducted from your sending limit.

Announce Lists

If you need to routinely send e-mail to a large number of recipients we would strongly recommend that you set up an Announce List via our control panel specifically for that purpose. You'll find that it makes dealing with large groups of subscribers very easy and don't have to worry about sending limits/quotas! Our Announce List feature manages the opt-in confirmations for you which complies with our Anti-Spam policies.

If you would like to set up an Announce List via our control panel go to (MAIL > ANNOUNCE LISTS).

See this DreamHost Announce List Wiki article for more information.

Viruses Spyware & Adware

Viruses, spyware and adware can sometimes infect your computer and send e-mail to everyone in your e-mail clients address book! Or they may just use your e-mail account to send out their spam messages. These sending limits help to curtail the amount of "damage" done by these terrible breaches. If you know that you have not exceeded your sending limits but receive the error "SENDER QUOTA REJECTION" then contact support. Give us the e-mail address/username that is being blocked and we can review the mail logs to determine what has happened. It could be that e-mails have been sent through your e-mail account without your knowledge. If that happens you'll need to run virus, spyware & adware scans to clean up your computer.

Important Notes

  • If you have an account set to forward any e-mails to an another address, those forwarded messages also count towards your sending limit.
  • If you have Keyword Filters on an account that are set to forward any e-mails to an another address, those forwarded messages also count towards your sending limit.
  • Auto-responder messages also count towards that accounts hourly sending limit.
  • If you have Cron jobs running that send e-mail they will count towards that shell accounts hourly sending limit. Cron job completion/error notification e-mails count too!
  • Multiple websites hosted under the same FTP/shell account that send e-mail all count towards that FTP/shell accounts sending limit!
  • Cron jobs and other scripts/CGI processes that use authenticated SMTP to send e-mail message will be restricted to the sending limit of the address that they use for authentication.

Incoming Message Limitations

  • The sending limits do NOT apply to incoming messages! Just for completeness, here are the (2) incoming message limitations.
  1. Max 40MB message size. Incoming message over 40MB will be bounced!
  2. The amount of disk space you've allocated to your mailbox! That's right, if your mailbox fills up it will cause incoming messages to be bounced! You probably won't even be able to delete any messages either because the server needs some free space to work. So DON'T LET YOUR MAILBOXES FILL UP! See the Email_Setup article for more information on setting the "Limit total disk usage" and "Email me daily" warning messages for your accounts.
  • We recommend allocating at least 100MB for each mailbox. With a 40MB message size limit just a couple of large message could fill your inbox!
  • We recommend enabling the "Email me daily" warning messages for your accounts! This will help keep you out of trouble.
  • If you have the "Save removed messages" option enabled (which is the default option), those saved messages can eat up your disk space without you ever seeing them! Make sure that you've subscribed to the "old-messages" folder (or whatever you've configured it to be) so you know what's in there.
  • If you have configured one of your FTP/shell accounts as the mailbox for your e-mail address and it's also used to store your web hosting directories the disk limit/quota applies to BOTH! Make sure that you take that into account when setting a disk limit! It's easy to shoot yourself in the foot by setting a limit that it too low. In most cases it's probably best not to set a disk limit for these types of accounts.

Log Output

If we do send you the output from our logs for your verification, here's how to interpret them.

The fields are as follows;

  1. Date & Time
  2. Throttle Status Code [See details below]
  3. Host IP Address of mail client (WebMail will show up as
  4. "From" Address
  5. "To" Address (could also be from CC or BCC field)
  6. Message Count - number of messages during this period / period limit (messages can have multiple recipients)
  7. Recipient Count - total during this period / period limit
  8. Threshold Info (percentages) the 3rd one is the only relevant one
  9. "sasl_username" (account used for SMTP authentication) (WebMail will not show this field)

[ignore numbers or letters in parenthesis in the log output]

Throttle status codes & meanings

  • "new" = Initial throttle start (first message sent beginning a new period)
  • "clear" = Throttle restarted (first message sent beginning a new period)
  • "update" = Update to throttle (current period in process)
  • "abuse" = Throttle exceeded. Account blocked until throttle period expires. No messages sent. See examples above.


-------1------- ------2--------- ---------3--------- ---------4------------- -----------5------------- 
Jan  2 07:40:47 throttle=new(a), host=,,, 
------6-------- ------7------- ---------8--------- ----------------9--------------
count=1/100(1), rcpt=1/100(1), threshold=0%|0%|0%,


See these links for more details on our policies;