Email error: 'There was an issue sending an email to this contact'

This message displays on a contact record when an email was not sent to the contact. A Not sent email is different from an email bounce. In these cases the email is never sent from HubSpot, so the email can't bounce.

HubSpot uses Not sent emails to preserve your sending reputation. The system will only block emails from sending if there's a high probability that the email will not be delivered or if it would be illegal to send an email to that particular contact. You may see Not sent emails for sales or marketing emails and additional messaging depending on the Not sent reason.

• This recipient looks invalid - previous sends to this address have bounced: this message appears when an email to the recipient has previously bounced. If this error appears for a one-to-one email addressed to multiple recipients, and one of the recipients previously bounced, HubSpot will not send the email to any of the email's recipients.
• A previous email to the recipient was flagged as spam: this message appears when an email to the recipient has previously been marked as spam.
• The recipient previously unsubscribed from this subscription type [specific email type]: this message appears when the recipient has opted out of that email type.
• The recipient previously unsubscribed from all subscription types: this message appears when the recipient has previously unsubscribed from all your email subscription types.
• The email address in the 'to' field failed validation: this message appears when the recipient's email address fails HubSpot's validation attempts due to a syntax error.
• This 'from' address looks invalid: this message appears when the sender's email address fails our validation attempts due to a syntax error.
• This company has opted out of all email types: this message appears when the company has explicitly requested to not receive emails from any HubSpot accounts.
• The recipient requested to not receive any emails via HubSpot: this message appears when an individual recipient reported an email from HubSpot as spam or has explicitly requested to not receive emails from any HubSpot accounts. This error also may appear if an email address is a known spam trap. To unblock this address from receiving emails, you'll need to provide proof that the contact is legitimate and wants to receive emails.
• This recipient has bounced: this message appears when the recipient is globally bounced.
• The recipient is invalid: this message appears when the recipient's mailbox cannot be reached. Possible reasons for this error are:
  • The recipient's account no longer exists or has been blocklisted.
  • The domain does not exist or has been improperly configured. Confirm that the email address is correct before attempting to send to the contact again.
  • The recipient's address originates from a known disposable domain that HubSpot automatically blocks due to the high likelihood that the email will bounce. 
• This recipient's domain was blocked: this message appears when there is an explicit request from the owners of the domain to not receive any email sent from HubSpot accounts.
  
• The recipient has not yet confirmed their subscription: this message appears when the email cannot be sent because the user hasn’t confirmed double opt-in.
• This email send was cancelled: this message appears when the user cancels the email send.
• This email wasn’t able to be delivered: this message appears when HubSpot's Mail Transfer Agents (MTAs) fail to deliver the email for any number of reasons.
• This email wasn’t sent: this message appears when the contact cannot be sent an email and HubSpot was unable to determine a specific reason for the failure. 
• The recipient was suppressed due to the send frequency cap: this message appears if you've already sent the contact the maximum number of marketing emails for the month, as designated in your email settings. This feature is available to Marketing Hub Enterprise accounts only.
• Your account has gone over its monthly limit for email sends: this message appears when you've exceeded your email provider's cap on monthly emails.
• Your account was suspended for non-compliance or deliverability issues: this message appears if you've previously violated email policies.
• The email address in the 'to' field failed validation: this message appears when you try to send to a role based email address, such as support@mycompany.com or sales@mycompany.com. This message will also appear if the email address you entered is misspelled, invalid, or fake.
• Recipient was suppressed due to low engagement: HubSpot will avoid sending email to unengaged contacts to help you maintain a healthy email sending reputation. Learn more about graymail and unengaged contacts.
• The user who scheduled this email was deleted: this message appears when the user who originally scheduled the one-to-one email was removed before the scheduled send time.
• You have hit a send limit with your provider: this message appears when your provider reports that you've sent too many emails in a given time period. Each provider enforces different sending limits, so it's recommended you wait at least a day before sending again, or you can contact your provider to increase the limit. Learn more about email sending limits.
• The recipient's mailbox is full: this message appears when the recipient's mailbox is full and cannot accept any new messages.
• Your provider has suspended your inbox: this message appears when your email provider has suspended your ability to send emails from your account. You'll need to work with your provider or your company's IT admin to resolve the issue.
• Your inbox connection failed: this message appears when HubSpot received a connection error from your mail server. If the issue persists, you'll need to work with your email provider or your company's IT admin to resolve it. Review the technical requirements for connecting your inbox.
• Your inbox authentication failed: this message appears when HubSpot received an authentication or permission error when attempting to send the email. Try reconnecting your inbox and sending your email again. If the issue persists, you'll need to work with your email provider or your company's IT admin to resolve it.
• The email was classified as spam by the recipient's email server: this message appears when the recipient's mail server categorizes the email as likely spam.
• You have hit a sending permission error with your provider: this message can appear after your email is migrated from one Microsoft 365 tenant to another. To fix this issue, an admin in the Microsoft 365 tenant your email was migrated from will need to delete the HubSpot Sales app listed under Enterprise applications in Azure Active Directory.
• Request to Microsoft has timed out. Try again later: this message appears when HubSpot's requests to Microsoft to send your email time out. This can occur for a variety of reasons. Please try again at a later time. If the issue persists, check the HubSpot and Microsoft status pages.
• Request to email provider timed out. Try again later: this message appears when HubSpot's requests to your email provider to send your email time out. This can occur for a variety of reasons. Please try again at a later time. If the issue persists, check HubSpot's status page, along with the status page of your email provider.
• Email not allowed to be sent to the specified recipient in a sandbox or developer test portal: this error occurs when you're using the single send API, and you include a recipient who isn't a user in the sandbox or developer test account.
  • The email address you enter for a recipient is case-sensitive. Confirm the email address of your recipient exactly matches the address of an existing user in your sandbox or developer test account.
  • If needed, you can also resolve this issue by removing that user from your recipient list and retrying the send.
• The inbox that scheduled this email is disconnected: this message occurs when you originally scheduled an email to send at a future date from an inbox that got disconnected.