We are migrating to 365 (currently hybrid, based on each individual dept) and are struggling to understand the attachment size limitations that are in place. My understanding is that:
- each email can have a max of 25MB in attachments,
- no individual attachment can exceed 10MB,
- the limit includes the header info, and
- restrictions in place for either our Exchange 2003 users who haven't been migrated yet or for any other email system (gmail, msn, another entity, etc) also limit the total size.
We are seeing an "effective" limit of about 7.5 MB for a single email, regardless of the number of attachments or who sends them (365 or Exch user). Our consultant has advised us that this is due to the header info. We do have a 10MB limit in place on our old Exch 2003 server but have not knowingly imposed that in 365.
Please advise:
- how much header info (%) we should tell users to allow per email (or per attachment?), and
- for 365 users who are only exchanging emails with other 365 users in our FS, are they limited by our Exchange 2003 10MB limit ?
- If 365 users are being limited by our Exch 2003 restriction, can we change that during this hybrid phase ?
Thanks for your help.