Increasing Maximum Message Length for Inbound SMTP
Overview
When using SMTP paging, customers may find the default message length of 999 characters limiting, and may request to change that value to allow for additional text.
Goal
This article will describe the process for increasing the maximum message size length for inbound SMTP. A basic understanding of how to edit text in Linux (using VI for example) and how to reset processes is assumed.
First Step
It's likely that the customer has at least a specific minimum message length in mind. While the default limit is configured as 999 characters, the actual hard limit based on the size of the message table is 4000. In order to reserve room for header information etc., it's extremely advisable to leave some room below that maximum. Find a value that the customer is comfortable with, taking into consideration the capabilities of the receiving devices. I would suggest a "real world" maximum of 3900 characters or less, although if a receiving pager only supports 250 characters, that should be factored into the decision making (indeed, the message length may need to be decreased instead of increased in such an instance). Attempting to send a page over the maximum supported by the receiving pager would simply result in the default callback message as defined by the Class of Service configured for the device.
Second Step
Determine which servers are running the smtp_in process. Note this change will be required on any server that is running the process in order to ensure the changes are consistent and working regardless of which server processes the smtp_in connection.
Third Step
Back up the smtp_in.ini file, found in the /home/amcom/ folder.
Fourth Step
Using VI (or another text editor), edit the smtp_in.ini file, changing the following keyword:
MAXIMUM MESSAGE LENGTH=999
to
MAXIMUM MESSAGE LENGTH=3900
(or whatever the new maximum should be)
Save that change and exit the text editor.
Fifth Step
With customer's permission, restart the smtp_in process.
What's Next
At this point, the message size limit should be successfully changed. Be sure to make the change on any additional servers that may be running the smtp_in process. Finally, have the customer test this increased limit (by sending an SMTP page with a significantly large character count) to ensure that the change is working as intended.