Email issues
At Arivisti, Technical Analysts will get asked this question many times. Unfortunately the question
is a little vague since there are really hundreds of reasons why an email may not get delivered.
These can be:
Authentication issues (the most common).
DNS related issues (is your rDNS set up correctly?).
SPF, DKIM and/or DMARC settings (misconfigured or missing completely).
Firewall issues (or proxying of port 25 by the NOC, Datacenter, Host or customers ISP) or other networking issues.
Blocked IP addresses (Customers IP address may be blacklisted).
cpHulkd brute force lockouts.
SpamAssassin settings too strict.
Spammer (or more likely a compromised email account) has filled up your exim mail queue with spam messages and legit messages are now waiting to be sent.
Exim misconfiguration.
Sender Verify and even Greylisting or other temporary soft-errors.
An incorrect setting within your /etc/resolv.conf file.
A misconfigured filter.
Mailbox is over quota (5.2.2. error).
Virus was attached to message and virus scanner redirected your email to /dev/null.
When you're troubleshooting email delivery for a client, the one thing you want to avoid is the proverbial "mess of potholes" and the root cause may be anything from being over-quota in the mailbox to having a strict SpamAssassin filter.
While I was mixing with my vape mods earlier, I was paging through the list and it really does show how multi-layered Exim setups can be, particularly if there's a cpHulk lockout in place, or a SPF/DKIM misconfiguration. For any tech-support team, the presence of this kind of checklist makes narrowing down any port 25 or DNS problems a lot easier.
sadsadasa
0850 346 78 12
