Recently my mail gateway email stuck at queue mail when sending bigger size email to yahoo From the event log, it showed event log: 451 Resources temporarily not available - Please try again later [#4.16.5] Information retrieve from Yahoo postmaster FAQ This error indicates that our servers were busy and temporarily unable to process your transaction at the time of connection. Such issues are generally brief, and normal connectivity is usually restored after a short period of time. There is no need to contact us regarding this error. On the checking, Yahoo ehlo result returned 250-size 41943040 It seems that yahoo put bigger size mail unlimited wait response, i want to confirm is the email delivery email to yahoo should not exceeed the ehlo size mentioned above, 4MB ?

Looks like some thing else. Its not the attachment of more then 4 MB is creating the prob. Try this. Create a SMTP connector only for yahoo and directly send email to yahoo (no smart host). See if you can send emails of more then 4 MB.Raj

Hi, On the Yahoo side, maybe there has the corresponding setting to deferr the big size email when smaller email is processed at the same time. Thanks Allen