421 SMTP Server error: too many concurrent sessions, please try again later.

[Jeff75]

Does anyone know what would cause this error "421 SMTP Server error: too many concurrent sessions, please try again later.? Any idea how to fix it? I tried restarting the mail server but it keeps coming up from time to time for a certain user when he sends mail.

[webignition]

421 SMTP Server error: too many concurrent sessions, please try again later.

This error seems rather self-explanatory - connections to the SMTP server are being rejected due to there already being X number of connections from the same IP.

Have you investigated the case that the user simply has too many open connections to the SMTP server?

[Jeff75]

I wasn't sure if this was either from too many users (total on the server) connecting to it, them sending out too many emails within an hour, or from them checking their email too many times. Here are my settings in WHM:

The maximum each domain can send out per hour (0 is unlimited):160
he number of times users are allowed to check their mail using pop3 per hour. Zero is unlimited:180

[Gopi]

Hi Jeff,

Where to set this??????

"he number of times users are allowed to check their mail using pop3 per hour. Zero is unlimited:180"

[cpanelkenneth]

Hi Jeff,

Where to set this??????

"he number of times users are allowed to check their mail using pop3 per hour. Zero is unlimited:180"

Look in the Courier Configuration editor in WHM. The specific entry Jeff mentioned as pertinent only to the deprecated cppop service. However the Courier Configuration editor will allow you to set similar thresholds for the Courier service.