I am having trouble sending attachments over ~1.5 MB. Also applies to inserted photos, etc. This is not a provider server problem as the same providers webmail functions without issue. It is not an account configuration problem as text emails and smaller attachments go through. The size limitation is not rigid. Slightly larger files sometimes get through, up to 2.3 MB in my testing. Slightly smaller files sometimes fail, down to 1.3 MB in my testing. I get 2 different messages. The progress bar sometimes reaches 100%. In that case I get this message, "The message could not be sent using Outgoing server (SMTP) mail.XXXXX.net for an unknown reason. Please verify that your Outgoing server (SMTP) settings are correct and try again." When the transmission fails at less than 100% I get this message, "Sending of the message failed". I am using V 91.3.2 I have increased 'Offer to share for files larger than' from 5MB to 10MB with no apparent effect. Posts here have said to change specific timeout settings. I have been unable to locate a 'Connection Timeout' setting or a 'mailnews.tcptimeout' setting anywhere in this version.