Hi,
I have read the project and we can fix the issues with SASL in your postfix server. Hopefully, SASL mechanism will be there with the postfix and it may be corrupted. Through ssh access we can fix it and make your mails working fine.
We are a team of professional server administrators under skynats technologies having many years of experience in the field of Linux/Windows administration.
Kindly accept our bid and we can have a detailed discussion through chat. Hope to hear from you soon.
Thank you