Simple Mail Transfer Protocol (SMTP)

SMTP is a TCP/IP based protocol used to deliver e-mail messages from a client to a server and between servers. SMTP was first implemented in 1982 and remains mostly unchanged to the present. Communication is usually unencrypted and there is no mechanism for identifying the sender accurately. These shortcomings have lead to many abuses including Spam and Identity Theft which have prompted many upgrades to SMTP but these have proven unsuccesfull

SMTP communication takes place on port 25 but most providers also accept connections from their clients on other ports such as 26 or 587. When a server receives an e-mail message it verifies if the recipient can be found locally. If the recipient is not local, the server performs a DNS check to find the Mail Exchanger (MX) for that particular domain and delivers the message to that server.

SMTP Authentication

PolarisMail has implemented SMTP Authentication in order to only allow its customers to relay e-mails through its servers. This option can easily be enabled in any modern e-mail client such as Outlook or Thunderbird and it uses the same username/password as for POP3 and IMAP. Without SMTP Authentication enabled and a valid PolarisMail account, you can not send remote e-mails through our servers.

PolarisMail fully supports the SMTP and ESMTP protocols on ports 25,26 and 587 for TLS or unencrypted communication and port 465 for the SSL version.

In order to not receive an SSL certificate warning when using the SSL version, you must use our servername , smtp.emailarray.com ,in your e-mail client configuration

SMTP Errors

SMTP Hard Error

An SMTP Hard Error is any error of the form 5XX such as 501, 510, etc. A hard error given by a server to a client means that the client should not attempt the same operation again. A hard error is usually returned when attempting to e-mail an invalid recipient or the e-mail message is unwanted by the server.

SMTP Soft Error

An SMTP Soft Error is any error of the form 4XX such as 401, 410, etc. A soft error returned by the server means that it's experiencing temporary difficulties and the sending client should attempt to deliver the e-mail again in the near future. Soft Errors might also be returned because of an active greylisting policy.