MTA warning: DNS-00398 dns_ares_query A failed: Out of memory

Products

• Messaging Gateway

Issue/Introduction

When reviewing the Messaging Gateway (SMG) mail server (MTA) logs you see multiple warnings indicating that a DNS query may have failed due to an out of memory condition but the system has plenty of RAM and is not making any or significant use of swap space.

2026 Apr 14 11:31:33 IST (warning) ecelerity: [1613066]DNS-00398 dns_ares_query A  failed: Out of memory

Cause

This warning does NOT generally indicate a memory issue for Messaging Gateway. The warning is a generic warning indicating some failure of the DNS resolver:

• The DNS response was malformed
• The DNS response was too large for the allocated buffer
• The DNS resolver has hit an internal retry limit and reports OOM as a fallback error

Resolution

If this warning is frequent or concerning you can pursue the following:

• Ensure that SMG is only using fast and local DNS servers for DNS resolution
• Avoid public or rate limited DNS servers (Google, Cloudflare, OpenDNS, etc)
• Ensure that DNS servers support EDNS0 correctly
• Disable DNSSEC in Administration > host > DNS / Time if there are DNSSEC errors