Changing MTU setting fixes problems sending email
Changing MTU setting fixes problems sending email
Frank Sauer and Michael Ford had previously alerted us to problems sending email with attachments via a Dual-Ethernet AirPort Base Station setup. This too turned out to be related to MTU settings, as noted in several Apple Discussion Boards threads (see one, two, and three, for example).
See also our previous coverage on MTU settings and routers - which notes that this problem may be restricted to PPPoE conections.
Update: A reader alerts us to this page, which also covers the MTU issue and provides a similar solution, using AppleScript.
John Strung adds: "I posted a MacFixIt Forums thread with detailed instructions on how to use the OS 9 version of IPNetTuner to set the MTU to 1492. For people using OS X who don't want to get involve in Unix commands, IPNetTunerX from may be a solution. Finally, for people using routers, the easiest solution might be to set the MTU in the router instead [Ed. note: as we discuss in the link cited above]."