The delay in e-mail delivery is usually only a few seconds unless the addressed server refuses to accept the respective e-mail, e. g. because of overload or for other errors. Known error messages (occurring frequently with the large free mail services) are e. g.:

- "too much load, try later" (server overload)
- "local error, try later" (server has serious problems)
- "mailbox full" (user mailbox is impeding delivery) 

In case of temporary errors on the opposite side common delays will result. Our server will then retry to deliver the e-mail numerous times (but with increasing time lags).