This is an issue of the PEAR Package and also PHPMailer which is used quite frequently.

About a year ago I was searching for a good email composing and sending class,
the result: SwiftMailer - http://www.swiftmailer.org/
Is used it several times, it's perfect. Fully OOP, Go PHP5.

Regarding the current issue let me quote from their website:
"Send attachments of any size even with PHP's 8MB Memory Limit"

So why not switch to SwiftMailer?

Balázs


Thomas Bruederli wrote: 
pete wrote:
  
Well, i deleted the message meanwhile :( When i tried to reproduce the
error, i raised the mem limit to 640M, and i tried to send a message with a
large 77Mb attachment to myself over Roundcube. 

The error message was in the log:
[22-máj-2008 11:07:59] PHP Fatal error:  Allowed memory size of 671088640
bytes exhausted (tried to allocate 208171409 bytes)
in /path-to-rcd-root/program/lib/Net/SMTP.php on line 788 
    

OK, this is another issue of the PEAR package which is unable to read from 
streams but composes all the message content in memory before it's passed 
to the SMTP server.
  
~Thomas

--
Horváth Balázs Balázs Horváth
Fejlesztési vezető Development Manager
WG Informatika Kft. WG Informatics Ltd.

H-1123 Budapest, Alkotás utca 53. (MOM Park, "D torony" II.em)
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E-mail: horvath.balazs@wgi.hu
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