diff --git a/Configure-DKIM.md b/Configure-DKIM.md
index 67db3e1..edd5038 100644
--- a/Configure-DKIM.md
+++ b/Configure-DKIM.md
@@ -100,4 +100,8 @@ mail._domainkey.domain.tld. 3600 IN TXT	"v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBA
 
 #### Switch off DKIM
 
-Simply remove the DKIM key by recreating (not just relaunching) the mailserver container.
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+Simply remove the DKIM key by recreating (not just relaunching) the mailserver container.
+
+#### Warning keys of 4096 bits
+
+Keys of 4096 bits could de denied by some mailservers. According to https://tools.ietf.org/html/rfc6376 keys are preferably between 512 and 2048 bits. See issue #1854.
\ No newline at end of file