Common error messages

Email is an old protocol with plenty of ways to fail. Most of the messages you get back are either rejections from the recipient's server, temporary problems that sort themselves out, or warnings from spam filters. Here's what you'll run into most often — and what to do about it.

Bounce messages ("Undelivered Mail Returned to Sender")

When an email doesn't get through, you usually get an automatic message back from the recipient's server. These are called bounces or NDRs (Non-Delivery Reports) — and they come in two kinds.

Hard bounce — permanent error

Examples you might see:

• 550 5.1.1 User unknown or Recipient address rejected — the recipient doesn't exist. Check that the address is spelled correctly.
• 550 5.1.2 Mailbox does not exist — the domain exists, but there's no mailbox with that name.
• 550 5.7.1 Message rejected with a reference to a blocklist — the IP address you're sending from is flagged as a spam source. Contact us at onmeil.eu/kontakt if this happens from an onmeil.eu address.

A hard bounce means you need to delete or fix the address before trying again.

Soft bounce — temporary error

Examples:

• 452 4.2.2 Mailbox full — the recipient's inbox is full. Wait and try again, or reach the recipient another way.
• 421 4.7.0 Try again later or 451 Temporary failure — the recipient's server is overloaded or down. onmeil.eu retries automatically for up to 24 hours.
• 421 Greylisted — the recipient has a spam brake that delays the first email from unknown senders. It goes through after a few minutes.

A soft bounce rarely needs any action from you — onmeil.eu retries automatically.

"Authentication failed" — wrong app password

If you've set up onmeil.eu in an email client (Apple Mail, Thunderbird, Outlook) and get the message "Authentication failed" or "Login incorrect":

1. Remember that you have to use an app password, not your login password
2. App passwords are entered without spaces (they're often shown as xxxx xxxx xxxx xxxx — remove the spaces)
3. If the app password is from before a password change, you need to create a new one under App connections
4. Check that username = full email address (fornavn@onmeil.eu, not just fornavn)

"Message too large" — attachment is too big

You'll see the error "Message size exceeds limit" or "552 Message size":

• onmeil.eu max: 20 MB per email (all attachments combined)
• Many recipients have even stricter limits (10 MB at some companies, 25 MB at Gmail)

For larger files, upload them under Files and send a share link instead.

Email lands in spam (yours or the recipient's)

Common reasons an email you send ends up as spam at the recipient's end:

• DKIM/SPF fails — usually not something you can fix yourself; let us know via onmeil.eu/kontakt if it keeps happening
• The content looks like spam — lots of links, known spam phrases, images only with no text, or ALL-CAPS in the subject
• You're sending to many recipients at once — large BCC lists get flagged by some filters

When you receive something legitimate in your spam folder, open the message and mark it as Not spam. The sender is remembered for next time.

See also: Spam.

Duplicates in the inbox

Getting the same email multiple times? Usually one of these reasons:

• The sender is on several distribution lists you're a member of
• A forwarding rule at the sender's end sends you the same message twice
• You've set up the same account in several clients without "read" status syncing — the message looks new in each client (but is only stored once in onmeil.eu)

If the duplicates have a different Message-ID, it's double sending at the sender's end. Same Message-ID means it's a client-side display thing, not actual duplicate mail.

"Connection lost" in your email client

Most common cause: an unstable internet connection. Secondary:

• The app password has been revoked after a password change — create a new one
• Your client is out of date — update to the latest version
• You've been temporarily locked out after many failed attempts — wait 15 minutes and try again

"Preferred server is down" / Status messages

Check status.onmeil.eu for known service notices. If nothing's listed there but you're having problems, send a message via onmeil.eu/kontakt — we'll take in the report and update the status page if it's something on our end.

When should you get in touch with us?

You don't have to guess or google forever — send a message via onmeil.eu/kontakt if:

• The same bounce happens repeatedly to a recipient you know exists
• DKIM/SPF errors show up in bounce messages
• Account login stops working with no obvious reason
• You see errors that aren't listed here

We'll reply within a reasonable time.