When sen ding out emails through Zoho Campaigns we get lots of bounces claiming that "mailbox name too long". The exact message varies from recipient server to server, but here are a few:

• 5.1.0 - Unknown address error 553-'MAIL FROM: mailbox name too long'
• Diagnostic-Code: smtp; 5.1.0 - Unknown address error 553-'MAIL FROM: mailbox name too long' (delivery attempts: 0)
• Diagnostic-Code: smtp;550 #5.1.0 Address rejected.

Given our actual from address is quite short, it must be the "envelope" address that they are rejecting. For example: bounce_21902661+117830934285f23_117830963202b6f_11699e4bf9d89b1_v1@zcsend.net

Is there a way to get around this? It's causing an unnecessarily high bounce rate.

Thanks.