Among all SMTP reply messages, error 550 is without a doubt the most well-known. It by and large accompanies a side-message like "550 Requested action not taken: mailbox inaccessible".
Basically, a 550 error code implies that your SMTP server can't deliver the sent email to the client since his mailbox does not exist: either the client has entered it wrong (a common case is something like firstname.lastname@example.org rather than email@example.com), or the account has been deactivated and replaced with another one (yet you didn't have any acquaintance with it).
Regardless, you should expel this address from your mailing list: continuing sending messages to it will trigger other 550 messages. This is not just irritating; it is perilous also for your deliverability. Actually, it certainly proposes to ISPs and receiving frameworks that you don't generally think about your list integrity - simply like spammers: so with time you could be punished and see your deliverance rate diminish.
Obviously the best practice here is not just to delete the address that incites a 550 error code, yet to replace it with another one at whatever point conceivable. How? If you have another approach to contact your client - a telephone number, Twitter, Skype - simply send him a line to notify him that his present email account isn't right, and to ask him a working one.
The uplifting news is that the SMTP error messages you have to stress over as an email sender are truly principally restricted to only a couple – those in the 5XX territory – and of those, the ones that you truly need to stress over are the ones in the 55X territory – i.e. 550-559. Of these, by a wide margin the most well-known one – the one that as a sender you will see frequently and to which you should give careful consideration – is the 550 SMTP error code, which can extend from "client not found" to "mailbox inaccessible”.
Back to that 550 error code. Quite often, when you recover an email bounced with a 550 error code, it implies that the receiving framework couldn't deliver your email to the client to whom it was tended to in light of the fact that the mailbox is inaccessible. Quite often, this implies the inbox either does not exist anymore, or that it never existed!
Why might you have an email address on your mailing list that has never existed? There could be a great deal of reasons, including that somebody entered it wrong, or that somebody deliberately entered a fake email address into your framework, (for example, when you require a client to give an email in order to get a download, and so on.).
Despite how it end up on your mailing list, in the event that you send a mailing to it, it tells the receiving framework one beyond any doubt thing: that you don't confirm email addresses before adding them to your mailing accounts.
What's more, in the event that you send email to that same non-existent email address in the wake of receiving the 550 message that the mailbox doesn't exist, it tells that receiving framework that don't you confirm email addresses, as well as that you couldn't care less especially about list cleanliness – i.e. that you don't keep up your mailing accounts as indicated by best practices, either.
Also, having decided this, soon those receiving frameworks, including ISPs, will essentially quit delivering your email to the inbox – first redirecting it to the garbage folder, then not delivering it by any means, and after that maybe notwithstanding blocking the greater part of your email.
The most effective method to settle Error 550
• What does Error 550 resemble?
Outgoing email error 550 – Relay not allowed
550 – Relay not allowed
• At what point when does Error 550 show up?
At the point when attempting to send email.
• Reasons for Error 550
When you attempt to send email through an email client and outgoing mail server confirmation is not on as a matter of course.
Step by step instructions to Fix Error 550
To settle Error 550, enable verification in the email client program:
Microsoft Outlook Express on Windows:
• Under Tools select Accounts
• Select account name > Click Properties
• Click the Servers tab.
• Check ‘My Server Requires Authentication’ check box.
• Select the ‘Use same settings as my Incoming Mail Server’ radio button.
• Click OK > OK, and afterward close.
Mozilla Thunderbird on Windows:
• Click Tools then Account Settings
• Look down and select Outgoing Server (SMTP)
• Click Edit (in the wake of selecting your Outgoing Server)
• Enable ‘Use name and password’ option.
• Type your full mailbox name as username, for instance: firstname.lastname@example.org
• Enter your email password for this email address, and click OK
Other email clients:
• Launch the email client.
• Find the options window.
• Find settings for SMTP mail server (otherwise known as Outgoing mail server)
• Check the checkbox which enables the SMTP server to get confirmation
• Enter your client name (email address) and password
• Click the ‘Use same settings as Incoming Mail Server’ radio button
• Save changes and close the window.