Email sending limit for mailbox

Spam protection mechanisms at mailbox

Email providers that allow anonymous registration unfortunately also attract the attention of spammers and other criminals. They either register free test accounts or misuse stolen credit card or PayPal data to open regular accounts.

mailbox therefore employs a variety of different techniques to prevent both such account openings and the sending of spam through these accounts. This is in the interest of all mailbox users, because by safeguarding the good reputation of our mail relays we ensure reliable delivery of all emails. This reduces the risk that emails sent from mailbox accounts are treated as spam by recipients.

Among other things, our systems evaluate a wide range of technical criteria when sending emails and calculate the probability of whether, for example, mass mailing is normal or whether it is a case of abuse. Factors such as the age of the account or the average email volume of the past few days are also included in these calculations. We cannot disclose the exact mechanisms and specific criteria in detail, otherwise spammers could adjust their behaviour to their advantage.

The various indicators are therefore combined in an overall assessment. If the result shows that the probability of account abuse is high, the email sending of this account can be temporarily blocked to protect everyone.

How many emails can I send per day?

It is not possible to say exactly how many emails an account can send per day. However, the following basic rules apply:

• An unpaid, newly registered test account allows up to 10 emails per day to mailbox addresses for testing purposes. Sending to external email addresses is not possible. To prevent abuse, we can only grant relatively low sending limits to unverified accounts. If you nevertheless try to send an email to an external address, you will receive an error message containing the note “Relay access denied”. As soon as a payment for the account has been received, this restriction will of course be lifted and it will be possible to send to external email addresses as well.

• Business customers have fixed contracts with us and are easier to authenticate as account holders. The risk of abuse through the use of stolen data to pay for account openings is thereby minimised. In addition, each business customer undergoes a careful manual review by us before activation. Therefore, we usually allow business customers 50,000 to 100,000 emails per day.

Error message “Relay access denied” when sending externally

If the following error message appears when sending emails to external addresses, this may be due to a number of reasons:

Message could not be sent to the following recipients: ..... 554 - 554 5.7.1 Relay access denied.

• Your account is still in the trial period: During the trial period, you cannot send emails to external email addresses. Once you have paid for a plan, your account will be activated for sending emails externally.
• You have already paid for a plan: In that case, this message is due to a different reason. Please open a ticket via https://support.mailbox.org.