Common causes of email problems

There are many possible causes why an email can’t be sent or delivered. If your message has made it to the recipients email provider, often you will receive a “bounce” email which gives clues to the problem. However, these messages are often technical or too cryptic to clearly explain the problem.

Here are some common reasons for failed messages:

Invalid email address

Often the cause is simple – the email address is invalid. This could be due to;

  • inclusion of spaces, foreign or odd characters, e.g. “joe”
  • a missing second part (domain), e.g. “joe.bloggs” instead of “”
  • wrong domain name, e.g. “” instead of “”

Not existent email addresses

Simply, you are sending to an email address which is no longer valid – typically the user has left the company.

Limited email account capacity

Another cause of an email failure is limited mailbox storage capacity of the recipient. When an email user hits their storage limit, it’s common that their incoming (and outgoing) emails are not accepted until they make more space available.

Blacklisted email addresses

Blacklisted emails are are email addresses which have been intentionally blocked – usually this relates to the email address (specifically the providers server) being linked to the distribution of spam email, however, sometimes innocent email addresses can be affected by a block.

Most of the time, blocks are only temporary, and the best thing to do with known blocks is to contact the provider; they will review the block and take the appropriate actions to remove the block.


Emails may also fail due to incorrect or missing SPF records. Please see our article on Sender Policy Framework (SPF) email validation for more information.

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