Titan Email
Titan Email is a hosted business email platform commonly resold by registrars and hosting providers for custom domains. Their SMTP responses frequently reflect recipient validation, sender authentication failures, anti-abuse enforcement, sender reputation checks, and inbound quota controls. Their team at support@titan.email is generally responsive to issues.
Links
Codes
- 421↑
421 4.7.0: Sender IP rejected: sending IP has insufficient reputation. Please retry later.
Your email couldn't be delivered because the sending IP address doesn't yet have sufficient reputation, as it's new in our system. This rejection is temporary—please try sending your email again later.
- 450↑
450 4.2.0 <user@example.com>: Recipient address rejected: greylisted: please retry after sometime
When an email is received from a suspicious IP address (often due to issues with reverse DNS), the server temporarily defers the message. The sending mail server is expected to hold the email for a short period before attempting to resend it. Subsequent retries from the sending server will then be accepted.
- 550↑
550 5.5.1 Protocol error
Error message indicating that there is a problem with the way the email is being sent, usually related to the protocol commands or their sequence.
550 5.1.8 <user@example.org>: Sender address rejected: Domain not found
Email rejected as no DNS MX and no DNS A record for the sender domain. These records specify the mail servers responsible for receiving emails on behalf of the sender domain. If an email cannot be delivered, a bounce message is sent back to the sender. Without proper MX and A records, the sender domain cannot receive these bounce messages, making it difficult to manage and rectify email delivery issues.
550 5.7.27 <user@example.org>: Sender address rejected: Domain example.org does not accept mail (nullMX)
Email rejected as a malformed MX record such as a record with a zero-length MX hostname found for the sender domain
550 5.1.1 <user@example.com>: Recipient address rejected: User unknown in virtual mailbox table
Recipient email address does not exist
550 5.1.1 <user@example.com>: Recipient address rejected: User unknown in local recipient table
Recipient email address does not exist
550 5.7.1 <user@example.com>: Recipient address rejected: Message rejected due to: SPF fail - not authorized.
SPF Hard failure : The SPF record for the sender domain specifies a set of IP addresses that are allowed to send emails on behalf of that domain. If the IP address of the sending mail server is not listed in the SPF record of the sender domain, and the SPF record explicitly indicates that the IP address is not authorized (e.g., through the "-all" mechanism), the receiving mail server will consider the email as a hard failure.
550 5.4.7 <user@example.com>: Recipient address rejected: Recipients Domain Hourly Quota Exceeded
Ratelimit exceeded https://support.titan.email/hc/en-us/articles/360038836914-How-many-emails-can-I-send-and-receive
550 5.4.7 <user@example.com>: Recipient address rejected: Recipients Domain Daily Quota Exceeded
Ratelimit exceeded https://support.titan.email/hc/en-us/articles/360038836914-How-many-emails-can-I-send-and-receive
550 5.4.6 <user@example.com>: Recipient address rejected: Recipient Quota Exceeded;
Ratelimit exceeded https://support.titan.email/hc/en-us/articles/360038836914-How-many-emails-can-I-send-and-receive
550 5.4.6 <user@example.com>: Recipient address rejected: Mailbox Does Not Exist : Domains Hourly Quota Exceeded;
Ratelimit exceeded https://support.titan.email/hc/en-us/articles/360038836914-How-many-emails-can-I-send-and-receive
550 5.4.6 <user@example.com>: Recipient address rejected: Mailbox Does Not Exist : Domains Daily Quota Exceeded;
Ratelimit exceeded https://support.titan.email/hc/en-us/articles/360038836914-How-many-emails-can-I-send-and-receive
550 5.7.1 message content rejected
Something in your message content was rejected by the filters. You can contact support@titan.email with details (To, From, Subject, Date) for more information.
550 5.2.1 <user@example.com>: Recipient address rejected: Incoming suspended due to abuse
This recipient domain is suspended due to suspicious activity , currently incoming emails are not getting accepted
550 5.2.1 <user@example.com> : Recipient address rejected: Incoming temporarily suspended due to partner migration
This domain is suspended due to ongoing partner migration, currently incoming emails are not being accepted.
550 5.7.2 <ip>: Sender IP rejected: spam rate exceeded
Your email was rejected because the sending mail server has been sending an unusually high volume of spam or suspicious messages. To protect our users, we block emails from servers that exceed safe sending thresholds.
- 552↑
552 5.2.2 user@example.com: Recipient address rejected: Quota exceeded (mailbox for user is full)
Titan enforces disk quotas to ensure that users do not exceed their allocated storage space
- 554↑
554 5.7.1 <user@example.com>: Relay access denied;
Recipient email address does not exist
554 5.7.1 Service unavailable; Client host [<ip>] blocked using b.barracudacentral.org;
IP address is found on an RBL, Titan rejected the email from that suspicious IP
554 5.7.1 command rejected
IP address is suspicious, Titan rejected the email from that suspicious IP