Fixing Email That Won't Send

Outgoing mail problems come in two flavours that need entirely different fixes: mail that will not send, and mail that sends but never arrives. Work out which you have before changing anything.

Mail will not send at all

If your client shows an error when sending, work through these in order:

• SMTP authentication is off. The most common cause by a wide margin. Your outgoing server must be set to require authentication with the same username and password as incoming.
• Username is not the full address. It must be you@yourdomain.co.uk, not you.
• Port blocked. Many ISPs block port 25 outright, and some block 465. Try 587 with STARTTLS.
• Mailbox over quota. A full mailbox can block sending as well as receiving. Check the quota in DirectAdmin.
• Sending limit reached. Hourly limits exist to stop a compromised account spamming. If you have hit one, that is usually worth investigating rather than working around.

Mail sends but never arrives

This is a deliverability problem, and it is almost always missing authentication records. Receiving servers are strict now: mail from a domain with no SPF or DKIM is routinely filed as spam or rejected outright.

Add an SPF record. A TXT record on @ containing v=spf1 a mx ~all covers a basic setup. Critically, you must have only one SPF record — two records invalidate each other, and this is a very common mistake when someone adds a second for a newsletter service. Merge them into one instead.

Enable DKIM. DirectAdmin can generate the keys and publish the record for you. DKIM signs each message cryptographically so the receiver can verify it genuinely came from your domain.

Consider DMARC. Once SPF and DKIM are working, a TXT record on _dmarc containing v=DMARC1; p=none; rua=mailto:you@yourdomain.co.uk tells receivers what to do with failures and sends you reports. Start with p=none and only tighten once the reports look clean.

Check your work

Send a message to a Gmail address you control. Open it, choose "Show original", and look for SPF, DKIM and DMARC each showing PASS. That view tells you precisely which one is failing, which saves a great deal of guesswork.

Several free services will also email you a report on your domain's authentication if you send them a test message.

If your domain is blacklisted

Usually the result of a compromised mailbox sending spam. Change the password on every mailbox immediately, check for forwarders you did not create, then request delisting from the relevant blacklist. Reputation recovers over days rather than instantly.

Suspected compromise is something to report to Traxio directly through the contact form, since it affects the wider platform.

If the cause turns out to be missing authentication records, the domain email guide explains SPF, DKIM and DMARC from first principles.

Reading a bounce message

When mail is rejected, the bounce (a “non-delivery report”) usually names the reason if you know where to look. Scroll past the boilerplate to the SMTP status code and the line of text beside it:

• 550 / 554 with wording about policy, spam or reputation — the receiver rejected the message on trust grounds. Check SPF and DKIM first; if those pass, check blacklists.
• 550 “user unknown” / “no such user” — the address genuinely does not exist. Check for a typo before assuming anything else.
• 552 or wording about quota — the recipient’s mailbox is full. Nothing on your side to fix.
• 451 / 421 “try again later” — temporary deferral, often greylisting of an unfamiliar sender. Your server retries automatically; if the same message defers for more than a day, treat it as a reputation problem.

The habit worth forming: paste the exact status line into a search before changing anything. Bounce wording is standardised enough that the first result usually diagnoses it.

Keeping your sending reputation healthy

Deliverability is easier to keep than to recover. The practices that matter on a small domain:

• Strong, unique passwords on every mailbox. Nearly every blacklisting starts with one weak password and an automated login sweep.
• Send transactional volumes, not bulk. Shared hosting mailboxes are for correspondence and site notifications. A newsletter to hundreds of addresses belongs with a dedicated sending service, which will also keep its reputation separate from your day-to-day mail.
• Keep SPF accurate as you add services. When you connect a form service or newsletter tool that sends as your domain, add its include to your existing SPF record — never create a second one.
• Watch your DMARC reports occasionally. A p=none policy with a reporting address costs nothing and shows you the moment something starts failing authentication.

Frequently asked questions

Why does Gmail accept my mail but Outlook.com junk it (or vice versa)?

Each large provider scores reputation independently, and a new domain starts unknown everywhere. Correct SPF, DKIM and DMARC plus a few weeks of normal, low-volume sending settles it. Asking recipients to mark one message “not spam” genuinely helps with that provider.

How long does blacklist delisting take?

The delisting request is usually processed within hours to a couple of days, but reputation with individual receivers recovers over days after that. Fix the cause first — a delisting with the compromise still active just gets you relisted.

Can I use an external SMTP relay instead?

Yes — transactional email services can send on your domain’s behalf, and for anything beyond light correspondence they are the more robust route. Add their SPF include and DKIM record when you connect one, per their instructions.

My contact form emails never arrive — is that the same problem?

Usually, yes: form plugins send mail from your domain, and without SPF/DKIM it is filtered like any other unauthenticated mail. Fix the records, and set the form to send to an address on a different provider (so a delivery problem on the domain cannot hide its own failure notifications).